Difference between #99 and #143 of Dynamic parent and child CGridView on single view. Using $.ajax to update child gridview via controller, after row in parent gridview was clicked.

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Dynamic parent and child CGridView on single view. Using $.ajax to update child gridview via controller, after row in parent gridview was clicked.
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dynamic, parent-child, CGridView, ajax, many_many, jquery event delegation,
loading.gif, CGridView sorting and filtering on default and related models, sort
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Content
This wiki has been updated on 21 May 2012 with the new **MODEL METHOD**.
Please note that the old **CONTROLLER METHOD** has been removed from this
document.

Message to beginners
--------------------
This wiki isI have been a step-by-step example
explaining how the controller, modeldesktop developer for ages, but
I'm new to Yii, OOP and the view's CGridView work
together.web development. It explains simple things - as
well as more complex things that you will anyway quickly havetook me
months to know. So, evenwrite this wiki, since I had to
start from scratch and work through several books with thousands of pages, and I
tried and tested a lot of different things. So if you don't use
dynamic gridviews,are also a beginner, take a morning off and
thoroughly work through this tutorial. It should give you a good start
and save you lotsweeks of
struggling.struggling - even if you don't use dynamic
gridviews.

Intro
-----
Forgive me for maybe “over-explaining” things a bit, which results in such a
lengthy wiki, but I think it could give beginners a better overall picture.
And 90% of the idea is to also cater for beginners.stuff
you have working already. So people who are in a hurry only need to
read the sections on 'The Process (in short)', the 'Views', the
'RoleController' and the 'Ajax' methods.actual new code is not that
much.

Many desktop programmers are used to having dynamic forms, where clicking on a
record in a parent sub-form, updates another sub-form with the child records. 
While having many levels of nested sub-forms in a single view might not be such
a good idea for a web application, I thought doing it one level deep might be
interesting and useful. But, instead of sub-forms I used CGridViews.

Major use case: Parent and Child CGridViews on single view
----------------------------------------------------------

### The Process (in short)

If you want to retrieve the child records for a certain parent record, then you
would NORMALLY just "read" one of the parent model's relations to the
child model. This is called "Relational Query" in the Yii
documentation.

However, in this example, we do not simply want to display the child records.
No, we need much more. We need to be able to manipulate (sort/search/page
and maybe even view/update/delete)(sort/search/page) the child
records in their own CGridView. But to do all this with the child records
in their own CGridView, they will need their own dataprovider.

So we do this by getting the child records DIRECTLY (not via relation
query)directly from their own model, where their own
dataprovider can beis generated.

So (in short) the process works like this:

1. The user clicks on a parent record in the
parent-gridview.parent-CGridView.

2. The parent record's primary key (PK) is sent from the view
(client) to the controller (server) - via our own Ajax function
(client).controller.

3. The controller renders the child-gridview and also passes
it the PK. Render meansPK to the following:
While being generated (on the server), the child-gridview
passeschild-model, which uses the PK to its own
child-model's search() function, where it is incorporated as a filter for
retrieving the relevant child records and storing them in a new
child-dataprovider. The child-gridview uses this child-dataprovider for its
rows. The child-gridview is then send to the
client.dataprovider.

4. On the client, our Ajax functionThe view receives the
new child-gridview from the serverdataprovider and
replacesupdates the old child-gridview
inchild-CGridView with the browser.new
records.

So here we go!
*********************************************************************************

### Database
In the database I have a classic many_many relation, which is broken/represented
by a junction table. 
The two outer tables are called "cap_role" (PK: role_id) and
"cap_permission" (PK: permission_id).
The junction-table in the middle is called cap_role_permission (PK:
rolepermission_id) (Unique: role_id, permission_id).
(Tables are prefixed by "cap_".)

<a href="http://www.flickr.com/photos/77396592@N06/7329386716/"
title="Many_Many by Gerhard Liebenberg, on Flickr"><img
src="http://farm8.staticflickr.com/7219/7329386716_5916cc6d92_b.jpg"
width="647" height="208"
alt="Many_Many"></a>

The idea is that you link permissions to roles (users will later be given
roles). So obviously, a role could have many permissions, and a permission could
also be assigned to many roles.

(Yii calls the direct relation between the two outer tables - with the junction
table between them - a many_many relation. But you still must have the junction
table in the middle! So there is no real many_many relation in the database.

Yii's many_many relation is thus simply a way of using one of the outer
table’s models, and then getting data directly from the other outer table –
without having to work “through” the junction table (like in sql). But in
the background Yii still works through the junction table, so you still need it
in the database. That is also why you will have to specify the
cap_role_permission table, as part of the many_many relation between the outer
tables.

The advantage of many_many relations is that it saves memory, because Yii
don't need to create additional model instances for the junction table's records
during a query.

HavingHaving said that, this wiki was updated in May 2012
to get the child records directly from their own model - without working
throughdoes not use the many_many relation any more.)

### Overview
I used the views/role/admin view for al the action. The parent-gridview displays
the default Role models. The child-gridview uses a different model - the
RolePermission model - to display the permission_id of the relevant
cap_role_permission records. In addition, the RolePermission model uses its
relation with the Permission model (normal "Relational
Query") to also display the permission_desc fields of the related
cap_permission records.

<a href="http://www.flickr.com/photos/77396592@N06/7235743956/"
title="DynamicGrids by Gerhard Liebenberg, on Flickr"><img
src="http://farm8.staticflickr.com/7237/7235743956_66cbbd4f44_b.jpg"
width="468" height="683"
alt="DynamicGrids"></a>

### Views
My views\role\admin.php view:

~~~
[php]
<h1>Manage Roles</h1>

<?php echo CHtml::link('Advanced
Search','#',array('class'=>'search-button')); ?>
<div class="search-form" style="display:none">
	<?php $this->renderPartial('_search',array(
		'model'=>$parent_model,
	)); ?>
</div><!-- search-form -->

<div id="parentView">
	<?php
		/*For the above "Advanced Search" function to work, keep the gii
		generated id for the parent CGridView. 
		In this case it is "role-grid". 
		If you do want to change it to something else - like parent-grid -
		then also change the name in the javascript 'search' function, that
		is normally located just above the "Advanced Search" function.

		Add the line: 'ajaxUpdate' => 'child-grid', to the parent
		CGridView (role-grid).role-grid. This ensures
		ensures that the child-grid is also
		refreshed refreshed when the role-grid is
		is sorted/filtered/paged via the 
		build-inbuild-in Yii ajax.

		How
		How does it work?:work: Ajax is suppose to update
only certain sections
		of a view (on the client), with data specific to that section,
		which is obtained from the controller and/or model (on the server).
		
		So ajax is about speed, because you don't need to wait for the
		entire page's data each time you want to update a section.
		
		However, Yii's ajax when doing gridview sorting, filtering and
		pagination works differently. In these cases, the entire view is
		still rendered to the client, but Yii then only refreshes the
		gridview and ignores the rest of the received data. For this
		reason, the default gii generated actionAdmin has only one
		render function, which renders the entire view - regardless of
		whether the event refreshes the whole page or actually needed only
		a section of the view. (This way of treating ajax, only pertains
		to CGridViews in gii generated controllers. You could change it if
		you want - since gii is only intended to give you a platform to
		start from. But I'm also sure it will be improved in future Yii
		releases.)
		
		In our example, when the role-grid gets sorted, 'ajaxUpdate' => 
		'child-grid' tells Yii to also extract the child-grid's data from
		the received view and to update it together with the role-grid.
		(If you have dynamic headings in the childView, or other data that
		also needs to be updated, then use 'ajaxUpdate' => 'childView'.
		This will update the entire childview with all its
headings,heading as well
		as the child-grid inside the childView.)
		Please note that 'ajaxUpdate' is part of the build-in Yii ajax.
		It is NOT part of our own custom ajax function (GROUP B 3.1 in the
		actionAdmin of the RoleController), which we will use to only
		retrieve data for the child-grid, and update only the child-grid,
		after a row in the role-grid was clicked.*/
		$this->widget('zii.widgets.grid.CGridView', array(
			'id'=>'role-grid',
			'dataProvider'=>$parent_model->search(),
			'filter'=>$parent_model,
			'columns'=>array(
				'role_id',
				'role_desc',
				array(
					'class'=>'CButtonColumn',
				),
			),
			'ajaxUpdate' => 'childView', //or 'ajaxUpdate' =>
'child-grid''child-grid',
		));
	?>
</div>

<!-- Use this paragraph to display the loading.gif icon above the Child
Gridview,
while waiting for the ajax response -->
<p id="loadingPic"></br></p>

<!-- The childView <div>, renders the _child form, which contains the
Child Gridview.
The ajax response will replace/update the whole <div> and not just the
gridview. -->
<div id="childView">
	<?php
		$this->renderPartial('_child', array(
		'child_model' => $child_model, 
		'parentID'/* New */
		'parentID' => $parentID, /* New */
		))
	?>
</div>

<?php
	/*Load the javascript file that contains our ownthe ajax
function*/
	$path = Yii::app()->baseUrl.'/js/customFunctions.js';
	Yii::app()->clientScript->registerScriptFile($path,
	CClientScript::POS_END);
?>
~~~

The following _child.php form contains the Child CGridView.
The gridview receives a dataprovider using the
searchIncludingPermissions($parentID) function in the RolePermission model. The
same function is used for filtering and sorting. (Note that the controller sets
$child_model to refer to the RolePermission model and not to the default Role
model).

Under the gridview’s columns we have the RolePermission model’s
permission_id and the related Permission model’s permission_desc. Since
permission_desc is a related field with sorting and filtering enabled, it should
be specified in this special way.

Note that the buttons in this gridview have been customized to use the child
records' controller (RolePermissionController) and not the default
RoleController. 
If you think this will confuse the user, take them out. However, I think it
could be a lovely feature if you have, for example, school classes in the
parent-gridview and students in the child-gridview. By clicking on a class in
the parent-gridview, the child-gridview displays a list of the students in that
class and you can immediately update a student's details by clicking the update
button in the child-gridview.
Having said that, I would only have 'update' buttons in the child-gridview,
otherwise it could get confusing. You can also link these buttons to the
PermissionController if required.


To only show the 'update' button, change the template to the
following:'template'=>'{update}',

You can read more about this here:
[CButtonColumn](http://www.yiiframework.com/wiki/106/using-cbuttoncolumn-to-customize-buttons-in-cgridview/
"")


The first paragraph uses the subsectionheading CSS class. You can obviously
change that to your own CCS class.
~~~
[php]
<p id="subsectionheading">Permissions linked to the above
selected Role</p>
<div class="hint">(Please note: If no Role is selected, the
Permissions of the top-most Role are displayed.)</div>

<?php
	$this->widget('zii.widgets.grid.CGridView', array(
	'id'=>'child-grid',
	'dataProvider'=>$child_model->searchIncludingPermissions($parentID),
	'filter'=>$child_model,
	'columns'=>array(
		'permission_id',
		array(
			'name'=>'permission_desc_param',
			'value'=>'($data->relPermission)?$data->
				relPermission->permission_desc:""', /* Test for
				empty related fields not to crash the program */
			'header'=>'Permission Description',
			'filter' => CHtml::activeTextField($child_model,
			'permission_desc_param'),
		),
		array(
			'class'=>'CButtonColumn',
			'template'=>'{view}{update}{delete}',
			'viewButtonUrl' => 'array("rolepermission/view",
			"id"=>$data->permission_id)',
			'updateButtonUrl' => 'array("rolepermission/update",
			"id"=>$data->permission_id)',
			'deleteButtonUrl' => 'array("rolepermission/delete",
			"id"=>$data->permission_id)',
		),
	),
));
?>
~~~

### CSS
The CSS for the paragraph displaying the loading.gif icon (this is toggled in
our ajax function). You can find a loading.gif file in your local Yii
installation:
~~~
[php]
.loadGIF {
	background: black url(/main/sub/css/images/general/loading.gif) left center
no-repeat ;
}
~~~

### The RoleController

To understand what is happening in the RolePermission model, you first have to
know what the controller is doing. Hence my lengthy comments:

The~~~
[php]
	public function actionAdmin()
	{
		/* The Parent CGridView in the admin view is called 'role-grid',
which
		which is Yii's default id for the CGridView displaying the Role
models.
		models. The Child CGridView is called 'child-grid'.

When a row in role-grid is clicked, our custom ajax function extracts the row's
primary key and stores it in a variable called	parentID, which is then passed to
this actionAdmin.

However, this actionAdmin is called by quite a few other events/functions (done
by Yii) as well, but not all of them also	pass the stored parentID to
actionAdmin.
		
Thus,		When a row in role-grid is clicked, our custom ajax
function
		extracts the row's primary key and stores it in a variable called
		parentID, which is then passed to this actionAdmin.
		
		However, this actionAdmin is called by quite a few other
		events/functions (done by Yii) as well, but not all of them also
		pass the stored parentID to actionAdmin.
		
		Thus, I have divided the events into Groups A and B:
	
GROUP		GROUP A	(Events that DO NOT pass parentID to
actionAdmin):
			
	At			At all times:
	1.1	Initial rendering/refreshing
			1.1	Initial rendering/refeshing of the 'admin' form,
		displaying
				displaying both role-grid and child-grid;
	1.2	role-grid
			1.2	role-grid sorting (Yii ajax),
	1.3	role-grid
			1.3	role-grid filtering (Yii ajax),
	1.4	role-grid
			1.4	role-grid pagination (Yii ajax).
			
	Only			Only BEFORE any role-grid data row was
clicked:
	2.1	child-grid
			2.1	child-grid sorting (Yii ajax),
	2.2	child-grid
			2.2	child-grid filtering (Yii ajax),
	2.3	child-grid
			2.3	child-grid pagination (Yii ajax).
	
GROUP
		
		GROUP B	(Events that DO pass parentID to actionAdmin):
			
			At all times:
			3.1	role-grid clicking (own custom ajax function).
			
	At all times:
	3.1	role-grid clicking (own custom ajax function).
	
	Starting			Starting only AFTER any role-grid row was
clicked:
	4.1	child-grid
			4.1	child-grid sorting (Yii ajax),
	4.2	child-grid
			4.2	child-grid filtering (Yii ajax),
	4.3	child-grid
			4.3	child-grid pagination (Yii ajax).

Note		Note that 4.1 - 4.3 are the same events as 2.1 -
2.3, but they	onlythey
		only start passing the parentID
afterparentID	after a data row in the
role-grid	wasrole-grid
		was clicked. Again, these are all Yii events and we don't have
control
		control over how they are functioning (unless you want to
change	thechange
		the Yii	files). So, we only have control over what 3.1 is doing,
but
		but for	the rest - we have to cater for their
behaviors.behaviours.*/

*When		/*When actionAdmin is used by any of the above
events, we don’t	knowdon’t
		know which event it is. Weis and we don't know if it is
the first time
		actionAdmin is being used by that event.
		We also don’t know if the user has entered any text (filtering
parameters)
		parameters) in the gridview’s “search” textfields, which should
be used
		used to filter the column’s data.

To		To prepare for all these
possibilities,possible scenarios, gii generates the
standard
		standard actionAdmin functions to do more or less the following:

**Process1:** Create		Process1:
			Create a single model instance (let's call it the filtering-model)
and put it in
 the 'search' scenario.
 (It only puts the model in the 'search' scenario. It does not execute the
model's
 search() function yet. More about scenarios in the RolePermission model.)


Empty the model from all default values, because we are going to use this
model which to store the user's
			user’s filtering criteria as well as our own filtering criteria.
So we don't want any default values to interfere with the filtering.

 (In this example the filtering-models are called $parent_model and $child_model
 respectively.)

**Process2:** Testparameters – if any.
		Process2:
			Test if the event currently using actionAdmin, passed
anyit 
			any filtering parameters
 that that the user might have entered. If
			If such parameters are found, store them in the
 newly created filtering-model.

**Process3:** Render newly 
			created model instance. 
		Process3:
			Render the view and pass it this single model instance.
		
		In the filtering-model - which now contains the user's
 filtering parameters, but does not form part of the data records
forview and model, the gridview.

**Process4:** Thefollowing happens:
		Process4:	
			The view renders the gridview,

**Process5:** which executes
		Process5:
			which passes this single model instance to the
filtering-model's
			model’s search() function,

**Process6:** which
		Process6:
			which incorporates the filtering-model'sfiltering
parameters into a dataprovider

**Process7:** and
			dataprovider
		Process7:
			and returns the dataprovider to the gridview to use for
dataas 
			data records.
	
So if we use "$this->" in the model's search() function, we
are actually referring to the filtering-model instance, which contains the
user's filtering parameters and which was passed to the view by the
controller.		(I hope I have that right, but I think it is pretty
close.)

And that is exactly why - in the search() function - we can have a
statement like:

 $criteria->compare('field1', $parent_model->field1, false);

This statement instructs the dataprovider to only include records where

 field1 = the value of field1 in the filtering-model ($parent_model).

So if the user enters a value in field1 on the CgridView, that value will end up
in the filtering-model (Process2 in the controller), which is used in the
model's search() function (executed by CGridView in the view - Process5) to
filter the records of the new dataprovider (Process6), which will update the
CGridView's data rows (Process7). 

This wiki's		This actionAdmin has a few additional
tests/processes and it works with
		with two models, but the basic functioning is the same.

It is also important to know that, besides from the user's filtering parameters
that we store in the filtering-model, we can also store	our own values in this
model instance, which we can then use to further influence the filtering of
records in the dataprovider.
We can even declare additional variables in the model - or pass	additional
parameters directly to the model's search() function -	to use as filtering
parameters.

Examples of such additional parameters in this wiki are:

1. the record id of a clicked row in the parent GridView, PASSED in a variable
called parentID, and used to filter the child records;

2. special variables DECLARED in the model, used to filter the gridview on
fields from RELATED records (fields not automatically part of our
filtering-model).

~~~
[php]
	public function actionAdmin()
	{same.*/
		
		
		/* Process1:
		CreateCreate a single
filtering-modelparent-model instance (placing it
in(using the
		'search' scenario), Role model's
		search function), which will hold the role-grid's filtering
		parameters entered by the user.*/user (not the	gridview's data
records).*/
		$parent_model = new Role('search');
		
		/* Empty the newly created filtering-modelparent-model
instance to clear all
		default parameters.*/
		$parent_model->unsetAttributes();
		
		/* Process2:
		TestTest if the event that is currently calling this action,
passed
		any filtering parameters that the user might have entered in the
		role-grid.
		If true, store these parameters in the newly created
filtering-modelparent-model
		instance. */
		if(isset($_GET['Role']))
			$parent_model->attributes=$_GET['Role'];
		
		/* Test if the event that is currently using this action, is from
		Group A or B */
		if(!isset($_GET['parentID'])){
			/* The event using this action now, is from Group A:*/
			$group = "A";
			
			/*The parentID was not passed to the controller and since
			we do not know which event is currently using actionAdmin
			(could be refreshing, sorting, paging, etc.), we do not
			know what records to display in the child-grid.
			So we need to find out which record will next be displayed
			at the top of the role-grid - considering all the
			filtering parameters (stored in our single parent-model
			instance) that we might/might not have received	from the
			event.
			
			Then we need to extract that top record's PK so that we
			can pass it to the view	to use it to generate the child-
			gridview's dataprovider.
			
			So the easiest way of doing this is to copy-cat the
			model's search() function (which will be used to generate
			the role-grid's real dataprovider).
			
			I thus created a temporary dataprovider in the controller,
			in which I incorporated all the filtering parameters
			received from the event - if any.
			
			NOTE: This way of obtaining the role-grid's first 
			record-to-be, could most probably be done in another way.
			For example: 
			I tried to extract the first record from the real 
			dataprovider after it was generated in the model 
			(Process6). But the problem is that you cannot then pass
			control back to the controller to continue testing how the
			child-gridview should be generated, because control has 
			then been passed to Process7, which renders the views.
			
			And if you want the view (in Process7) to render the child-
			gridview via another ajax function, that would probably
			result in a further round trip to the server. Creating
			a temporary dataprovider in the controller is much faster.
			
			And if you store the PK in the model or in the session 
			state during Process6, you still have to wait until one of 
			the events in Process7 calls the controller and passes it 
			the PK together with any new filtering criteria. However, 
			by that time the PK is OLD NEWS, because the new event 
			would normally result in a different first role-grid 
			record being needed.
			
			So for these reasons, I obtain the first record-to-be 
			directly in the controller, before the child-gridview is 
			generated. 
			
			(Note: I tried to limit the records in this dataprovider 
			by adding 'pagination' => array('pageSize' => 1,), but 
			since pagination then behaves differently from that
			of the real dataprovider in the model, the record-to-be
			would differ, resulting in the child-grid displaying the
			wrong records. So this dataprovider should be identical to
			that in the model's search() function.) */
			$criteria=new CDbCriteria;

			$criteria->compare('role_id',$parent_model->role_id,true);
			$criteria->compare('role_desc',
			$parent_model->role_desc,true);

			$dataProvider = new CActiveDataProvider('Role', 
				array(
					'criteria'=>$criteria,
				));
			
			/* Test if the dataProvider found any data (filtering 
				parameters might have excluded all records)*/
			If (count($dataProvider->getData()) > 0) {
				/* Extract the first model from the dataprovider */
				$first_model=$dataProvider->getData();
						
				/* Extract the record's PK, to be used to generate 
				the child-gridview's data records.*/
				$parentID = $first_model[0]->role_id;
			}
			else{
				/* Set $parentID to 0, to return an empty child-
				grid.*/
				$parentID = 0;
			}
		}
		else{
			/* The event using this action, is from Group B: */
			$group = "B";
			
			/* Get the parentID, which the event passed to this 
			action.*/
			$parentID = $_GET['parentID'];
		}

		/* Process1:
		Create another filtering-modelCreate a single child-model
instance which will hold the
		child-grid's child-
		grid's filtering parameters entered by the user.
		Putuser (not the 
		gridview's data records).
		To create this model inchild-model instance, use the
custom 
		searchIncludingPermissions function of the RolePermission model,
		passing it the searchIncludingPermissions
scenario.parentID. */
		$child_model = new 
			RolePermission("searchIncludingPermissions");			RolePermission("searchIncludingPermissions($parentID)");
		
		/* Empty the newly created filtering-modelchild-model
instance to clear all 
		default parameters.*/
		$child_model->unsetAttributes();
		
		/*If you later need to change this model's scenario		/*Put the
child-model instance in the searchIncludingPermissions 
		scenario. See the RolePermission model for whatever
		reason, you can do it like this. (Moremore details on
scenarios in the
		RolePermission model.)this 
		scenario. */
		$child_model->scenario =
'anotherScenario';'searchIncludingPermissions';
		
		/* Process2:
		TestTest if the event that is currently calling this action,
passed 
		any filtering parameters that the user might have entered in the 
		child-grid.
		If true, store these parameters in the newly created 
		filtering-model instance.child-model 
		instance. */
		if(isset($_GET['RolePermission']))
			$child_model->attributes=$_GET['RolePermission'];

		/* Process3:
		TestTest if the event that is currently using this action, is
from 
		Group A or B */
		if($group == "A"){
			/* GROUP A:		
			Render the 'admin' form while passing it $parentID and
			both filtering-modelmodel instances (containing the
user's
			and our own additional filtering parameters
			parameters - if any).
			(Remember, the
			The form's gridviews will also use the Role->search()
and
			RolePermission->searchIncludingPermissions(parentID)
			RolePermission->searchIncludingPermissions($parentID) 
			functions to create their own dataproviders.
			These functions will incorporate $parentID and any 
			received filtering parameters contained in the two
			filtering-models. model 
			instances.
			
			Note that the whole admin view is rendered (default gii
 			way of doing it), even if the event currently using this
			action might be	one of the Yii ajax functions (GROUP A, 
			1.2 - 2.3), which would normally only require a section of 
			the view. See the role-grid in the admin.php view for more 
			information on why the whole admin view is rendered. */
			$this->render('admin',array(
				'parent_model'=>$parent_model,
				'child_model'=>$child_model,
				'parentID' => $parentID,
			));
		}
		else{
			/* GROUP B:	
			Render only the '_child' form while passing it $parentID 
			and the single filtering-model (child-model) instance.
child-model instance (containing the user's 
			filtering parameters - if any).
			The form's gridview will use the
			RolePermission->searchIncludingPermissions($parentID)
			function to create it's own dataprovider.
			This function will also incorporate $parentID and any 
			received filtering parameters contained	in the single 
			child-model instance.*/
			$this->renderPartial('_child', array(
				'child_model'=>$child_model,
				'parentID' => $parentID,
			));
		}
	}


~~~

### Models

There is nothing special about the Role model, which will be used as default
model for the role-grid. So you can use the standard gii generated Role model.

There is no need to use the Permission model (for the cap_permission table)
since I'm directly obtaining the permission_desc field by using the
relPermission relation in the RolePermission model.

The RolePermission model looks like this:

~~~
[php]
<?php

class RolePermission extends CActiveRecord
{
	/* This variable is used to store the parameters enetered by the user for
	filtering the child-gridview's Permission Description column*/
	public $permission_desc_param;

	/**
	 * Returns the static model of the specified AR class.
	 * @param string $className active record class name.
	 * @return RolePermission the static model class
	 */
	public static function model($className=__CLASS__)
	{
		return parent::model($className);
	}

	/**
	 * @return string the associated database table name
	 */
	public function tableName()
	{
		return '{{role_permission}}';
	}

	/**
	 * @return array validation rules for model attributes.
	 */
	public function rules()
	{
		// NOTE: you should only define rules for those attributes that
		// will receive user inputs.
		return array(
			array('role_id, permission_id',	'required'),
			array('role_id, permission_id',	'length', 'max'=>10),
			// The following rule is used by search().
			// Please remove those attributes that should not be 
			searched.
			array('role_id, permission_id,
				permission_desc_param', 'safe', 'on'=>'search, 
				searchIncludingPermissions'),
		);
	}

	/**
	 * @return array relational rules.
	 */
	public function relations()
	{
		// NOTE: you may need to adjust the relation name and the related
		// class name for the relations automatically generated below.
		return array(
			'relRole' => array(self::BELONGS_TO, 'Role', 'role_id'),
			'relPermission' => array(self::BELONGS_TO, 'Permission', 
			'permission_id'),
		);
	}

	/**
	 * @return array customized attribute labels (name=>label)
	 */
	public function attributeLabels()
	{
		return array(
			'rolepermission_id' => 'Rolepermission ID',
			'role_id' => 'Role ID',
			'permission_id' => 'Permission ID',
			'system_record' => 'System Record',
		);
	}

	/**
	 * Retrieves a list of models based on the current search/filter
	conditions.
	 * @return CActiveDataProvider the data provider that can return the 
	models based on the search/filter conditions.
	 */
	public function search()
	{
		// Warning: Please modify the following code to remove attributes
		// that should not be searched.
		$criteria=new CDbCriteria;
		$criteria->compare('rolepermission_id',
			$this->rolepermission_id,true);
		$criteria->compare('role_id',$this->role_id,true);
		$criteria->compare('permission_id',$this->permission_id,true);
		
		return new CActiveDataProvider($this, array(
			'criteria'=>$criteria,
		));
	}
	
	public function searchIncludingPermissions($parentID)
	{
		/* This function creates a dataprovider with RolePermission
		models, based on the parameters received infrom the
filtering-model.
		It alsocontroller. It
		also includes related Permission models, obtained via the
		relPermission relation. */
		$criteria=new CDbCriteria;
		$criteria->with=array('relPermission');
		$criteria->together = true;
	
		
		/* filter on role-grid PK ($parentID) received from the 
		controller*/
		$criteria->compare('t.role_id',$parentID,false); 
		
		/* Filter on default Model's column if user entered parameter*/
		$criteria->compare('t.permission_id',$this->permission_id,true);
		
		/* Filter on related Model's column if user entered parameter*/
		$criteria->compare('relPermission.permission_desc',
			$this->permission_desc_param,true);
		
		/* Sort on related Model's columns */
		$sort = new CSort;
		$sort->attributes = array(
			'permission_desc_param' => array(
			'asc' => 'permission_desc',
			'desc' => 'permission_desc DESC',
			), '*', /* Treat all other columns normally */
		);
		/* End: Sort on related Model's columns */
		
		return new CActiveDataProvider($this, array(
			'criteria'=>$criteria,
			'sort'=>$sort, /* Needed for sort */
		));
	}
}

~~~

So what is happening in this model?

Normally CgridViews get their data records by using the model’s search()
function, which returns a dataprovider.

I did not want to amend the model’s search() function, because other
controllers need to use it as well. So I created a new function called
searchIncludingPermissions(). This function performs the same basic tasks as the
search() function, but it also:

1. includes the related permission records via the model's relPermission
relation;

2. filters the child records on the role-grid's PK ($parentID received from the
controller);

3. filters the child records on the user entered parameters (received from the
controller in the single child-model instance),

4. takes care of child-gridview sorting and pagination AFTER a row in role-grid
was clicked.

The searchIncludingPermissions() function receives the $parentID parameter
from the child-gridview, after it was passed to the view from the
controller.
 
The $criteria->compare('t.role_id', $parentID,false) statement filters the
child records - comparing their role_id to $parentID - only allowing an exact
match (false).
This filtering occurs regardless of whether the user included additional
filtering parameters.

The next two compare statements filter the user's filtering parameters – if
any:

$criteria->compare('t.permission_id',$this->permission_id,true);

“$this”“$this” refers to the single
filtering-modelmodel instance received from the
view,controller, so $this->permission_id will contain
any filtering parameters that the user might have entered in the
child-gridview’s permission_id column.
So the above statement compares the dataprovider (to be created) records with
the filtering-modelsingle model instance received from the
controller.

But there is a problem with the next compare statement:
The models to be created in the real dataprovider will have the following
structure:

- rolepermission_id

- role_id

- permission_id

- relPermission.permission_id

- relPermission.permission_desc

However, the filtering-modelsingle model instance
created by the controller to store the user’s filtering parameters, does
not have the same structure. It does not contain fields to store the user’s
filter parameters for the RELATED fields (due to lazy loading):

- rolepermission_id

- role_id

- permission_id

- relPermission

Therefore you can’t write the last compare statement like this:

$criteria->compare('relPermission.permission_desc',$this->relPermission->permission_desc,true);

So the answer to this problem is to create a separate public variable in the
model and use it to store the user’s filter parameter for the related column.
This public variable is declared at the top of the model, called
permission_desc_param.

Now we can use it in the compare statement:

$criteria->compare('relPermission.permission_desc',$this->permission_desc_param,true);


You can read more about this solution here: [Searching and sorting by related
model](http://www.yiiframework.com/wiki/281/searching-and-sorting-by-related-model-in-cgridview
"")

The permission_desc_param variable is also used in the child-gridview’s column
filter (see the child-grid in the _child.php view).

permission_desc_param also needs to be included in this model's safe rule.
This will ensure that it will also be assigned its correct value during Process2
in the controller - without us needing to specifically pay extra attention to
it.

Important: 
For the safe rule to also be applied to the searchIncludingPermissions function,
the rule must be amended to also work for the
"searchIncludingPermissions" scenario, and not just for the
"search"default search scenario.
array('..., permission_desc_param', 'safe', 'on'=>'search,
searchIncludingPermissions')
You will remember that the controller placed the child
filtering-modelsingle model instance in the
searchIncludingPermissions scenario.

Scenarios are simply used to enforce different model rules at different times.
You can read more about scenarios here: [Model rules
validation](http://www.yiiframework.com/wiki/56/reference-model-rules-validation
"")

### Our ownThe Ajax (passing
CGridView(extracting data from CGridView and passing
it to the controller)
**The ajax in the separately loaded javascript file - called
customFunctions.js**

### 1. Our own Ajax - Method-1 
**(Constantly displaying the child-records)**

**Different#### Different Javascript, Ajax and Jquery
options:** Ioptions
I first used the role-grid's own selectionChanged event to update the
child-grid, but that caused problems when the user clicked the same row twice,
since the second click deselected the same row that has just been selected by
the first click. This deselecting of the row caused
$.fn.yiiGridView.getSelection() not to be able to get the PK of the clicked
row, which meant that I could not constantly get the correct PK to
constantly display the child-grid.row. (This could be a good
option in some cases. See "Our own Ajax - Method-2"
below.)if you want the child gridview to disappear when the user
deselects a Role row or pages the role-grid. However, I wanted the child-grid
displayed at all times.)

I then used pure ajax with a function that checked the readyState from the
server’s response after the ajax call. However, the function worked fine in
Firefox but not in Internet Explorer 8.

After that, I used jquery's $('#role-grid table tbody tr').click(function(){.
This function binds a click event handler on all data-rows in the role-grid.
However, whenever the gridview was paged, these rows - and their assigned event
handlers - no longer existed. This behavior results in many questions on
the forum about things not working correctly after CGridView or CListView was
paged. Also see my example in one of these posts
[here](http://www.yiiframework.com/forum/index.php/topic/30000-clistview-style-jquery-are-not-working-after-pagination/page__gopid__202580#entry202580
"here").

I thusthen moved to using jquery's Event Delegation:
It binds an "on()" event handler to the parentView div, which is the
role-grid's parent.

This handler first watched for click events bubbling up when the user clicks one
of the gridview's data rows.
However, the rows also fired a click event if the user clicked one of the
buttons in the row - which is not what I wanted.

So finally, I changed the script to check for clicking events coming from a
row's columns (except the button-column).
The first line thus binds an event handler on the outer parent - the parentView
div.
This handler looks for click-events bubbling up from any data-row (tbody)
columns (td) that are not of class button-column (this is our own ajax in
the separately loaded javascript file - called
customFunctions.js).button-column.

~~~
[php]
$('#parentView').on("click", "table tbody
td:not(td:.button-column)", function(event){

	try{
		/*Extract the Primary Key from the CGridView's clicked row.
		"this" is the CGridView's clicked column or <td>.
		Go up one parent - which gives you the row.
		Go down to child(1) - which gives you the first column,
			containing the row's PK. */
		var gridRowPK = $(this).parent().children(':nth-child(1)').text();
		
		/*Display the loading.gif file via jquery and CSS*/
		$("#loadingPic").addClass("loadGIF");
				
		/* Call the Ajax function to update the Child CGridView via the
 		controller’s actionAdmin.*/
		actionAdmin */
		var request = $.ajax({ 
		  url: "Admin",
		  type: "GET",
		  cache: false,
		  data: {parentID : gridRowPK},
		  dataType: "html" 
		});

		/* Url Problems: 
		If you receive 404 errors about the request not finding the
		correct page or 'request failed' etc., then the above url is 
		probably not formatting	correctly. (Use Firebug to see if the
		generated url contains both the controller and the action names.)
		However, this error sometimes results from code in a totally 
		different location.
		
		For example: I got this error when I had the following line in my 
		urlManager in the config/main.php file:

		'<controller:\w+>' =>'<controller>/admin', //if no action is 
		provided, use actionAdmin

		When the user clicks on my CHtml::link to go to my actionAdmin 
		for the first time, the above line caused CHtml::link to not 
		include the action's name in the url in the browser's address bar.

		I guess the ajax-request uses the same url in the address bar to
		generate its own url.
		So make sure your url in the browser's address bar contains both 
		the controller and action names.*/

		request.done(function(response) { 
			try{
				/*since you are updating innerHTML, make sure the
				received data does not contain any javascript - 
				for security reasons*/
				if (response.indexOf('<script') == -1){
					/*update the view with the data received 
					from the server*/		
			document.getElementById('childView').innerHTML = response;
				}
				else {
					throw new Error('Invalid Javascript in 
					Response - possible hacking!');
				}
			}
			catch (ex){
				alert(ex.message); /*** Send this to the server 
				for logging when in production ***/
			}
			finally{
				/*Remove the loading.gif file via jquery and CSS*/
				$("#loadingPic").removeClass("loadGIF");
					
				/*clear the ajax object after use*/
				request = null;
			}
		});
		 
		request.fail(function(jqXHR, textStatus) {
			try{
				throw new Error('Request failed: ' + textStatus );
			}
			catch (ex){
				alert(ex.message); /*** Send this to the server 
				for logging when in production ***/
			}
			finally{
				/*Remove the loading.gif file via jquery and CSS*/
				$("#loadingPic").removeClass("loadGIF");
					
				/*clear the ajax object after use*/
				request = null;
			}
		});
	}
	catch (ex){
		alert(ex.message); /*** Send this to the server for logging when 
		in production ***/
	}
});

~~~

### 2. Our own Ajax - Method-2 
**(Displaying the child-records only when parent-row is clicked)**

As time goes by, you tend to add more complex features to your gridviews. A
feature that I added, enables the user to select the number of rows the gridview
should display (by adding a header with a dropdownlist to the CButtonColumn; and
then getting the dataprovider to incorporate this dropdownlist's value into the
pageSize.)

Obviously these kind of functionalities make it more difficult to 'calculate'
the first record-to-be in the controller. And if you add even more complexity -
such as displaying your gridviews in different CJuiTabs and in separate dialogs
- then the task of getting the first record-to-be in the controller, could
become quite difficult.

So, in these cases I made peace with the idea that the child-gridview can not
constantly display the child records. It only displays the child records after
the user clicks a row in the parent-drigview. For all other GROUP-A events, the
child-gridview is empty.

This is not all bad. The advantage of this is that we can now use
$.fn.yiiGridView.getSelection() to get the parent-gridview's PK. So we are not
forced any more to include the PK in the gridview's first column, because
$.fn.yiiGridView.getSelection() finds the PK regardless of whether it is
included in the gridview#### CHtml::ajax or not. 

Another advantage is that we don't need to 'calculate' the first record-to-be in
the controller any more, since the child-gridview is now only displayed with
GROUP-B events.

We also don't need JQuery's Event Delegation in our Ajax any more, because after
the user clicked a row, the parent-gridview can simply run our Ajax function by
itself.

So the controller's GROUP-A and GROUP-B testing section can become as simple as
this:

~~~
[php]
if(!isset($_GET['parentID'])){
	$group = "A";
	$parentID = 0; //Child-gridview will have no records
}
else{
	$group = "B";
	$parentID = $_GET['parentID'];
}

~~~

The parent-gridview can now do the job of calling our Ajax function (Jquery's
Event Delegation is not performing this job any more):


~~~
[php]
	$this->widget('zii.widgets.grid.CGridView', array(
		'id'=>'role-grid',
		'dataProvider'=>$parent_model->search(),
		'filter'=>$parent_model,
		'ajaxUpdate' => 'childView',    //or 'ajaxUpdate' => 'child-grid'
		'afterAjaxUpdate' => "updateChild",  // new code
		'selectionChanged'=> "updateChild",  // new code
		'columns'=>array(...
~~~


updateChild is the new name for our own custom Ajax function. Note that the
Event Delegation has been removed from the first line:

~~~
[php]
function updateChild(id, options)
{
	try{
		/*	Extract the Primary Key from the CGridView's clicked row */
		var myPK = parseInt($.fn.yiiGridView.getSelection(id));
		
		/* If $.fn.yiiGridView.getSelection(id) can not find PK, then return. */
		if(isNaN(myPK)){
			return;
		};
		
		/*Display the loading.gif file via jquery and CSS*/
		$("#loadingPic").addClass("loadGIF");
				
		/* Call the Ajax function to update the Child CGridView via the
		 controller’s actionAdmin */
		var request = $.ajax({ 
		  url: "Admin",
		  type: "GET",
		  cache: false,
		  data: {parentID : myPK},
		  dataType: "html" 
		});
		
		/* See "Url Problems" at this same location in 
		 "Our own Ajax - Method-1".*/

		request.done(function(response) { 
			try{
				/*since you are updating innerHTML, make sure the
				received data does not contain any javascript - for
				security reasons*/
				if (response.indexOf('<script') == -1){
					/*update the view with the data received
					 from the server*/
					document.getElementById('childDiv').innerHTML = response;
				}
				else {
					throw new Error('Invalid Javascript in Response - possible hacking!');
				}
			}
			catch (ex){
				alert(ex.message); /*** Send this to the server for
				 logging when in production ***/
			}
			finally{
				/*Remove the loading.gif file via jquery and CSS*/
				$("#loadingPic").removeClass("loadGIF");
					
				/*clear the ajax object after use*/
				request = null;
			}
		});
		 
		request.fail(function(jqXHR, textStatus) {
			try{
				throw new Error('Request failed: ' + textStatus );
			}
			catch (ex){
				alert(ex.message); /*** Send this to the server for
				 logging when in production ***/
			}
			finally{
				/*Remove the loading.gif file via jquery and CSS*/
				$("#loadingPic").removeClass("loadGIF");
					
				/*clear the ajax object after use*/
				request = null;
			}
		});
	}
	catch (ex){
		alert(ex.message); /*** Send this to the server for logging when in
				   production ***/
	}
}
~~~

Tip: If you don't want to display the empty child-grid, you can make the
childDiv invisible in the admin.php view.


~~~
[php]
<div id="childDiv" style="visibility:hidden" >
~~~

Then simply toggle the visibility in the above Ajax function with: 


~~~
[php]
$("#childDiv").css("visibility", "hidden"); or
$("#childDiv").css("visibility", "visible");
~~~

That should do the trick!

### Choosing between CHtml::ajax and $.ajax
You can either use CHtml::ajax or $.ajax (also called JQuery.ajax) (see
http://api.jquery.com/jQuery.ajax/ for more examples).

CHtml::ajax and $.ajax do the same job. However CHtml::ajax is a Yii based PHP
function. It must be stored in the view and not in a separate javascript file.

If you want to store your function in a separate javascript file, then use
$.ajax.

"Both CHtml::ajax and $.ajax will take care of browser inconsistencies and
will also help you with all the "readyState" and
"ActiveXObject" (pure ajax) stuff. You don't have to worry about such
things anymore, just focus on the interesting parts." (thank you for
clearing that up Haensel).

Personally, I prefer putting my functions in separate javascript files, because
it allows you to re-use your code. So if you give all your
parentDiv/parent-grids the same ID and all your childDiv/child-grids another
same ID, then the ajax function should work for all your parent-child views. If
you don't want to give them the same ID, but still only want a single ajax
function, then you will have to pass the ID to the function.

HaenselHaensel also mentioned that
$.ajaxit makes debugging easier. Some experts also say
that $.ajax gives you more control.

### 3. Using a button to do the ajax - Method-3
As time goes by, new or improved widgets are developed and shared between
developers.
An example of such is Clevertech's Yii Booster, Yii Bootstrap and Yii
Boilerplate family, 
based on Twitter Bootstrap and HTML5 Boilerplate (both will save you time in
future).

Yii Booster has a lovely extension on the CGridView which they call
TbExtendedGridView.
This gridview has lots of nice features including editable columns, column
totals and build in dynamic parent-child gridviews called
[TbRelationalColumn](http://yiibooster.clevertech.biz/extended-grid.html#gridcolumns
"TbRelationalColumn"). If you click on a button in the parent record,
a huge new row appears in the gridview, just below the parent record. In this
new row, an entire child-gridview appears with all the related records.

However, the technology is still new and I can't get the sorting, filtering and
pagination of this nested child-gridview working (most probably because the
child-records don't have their own dataprovider and are thus read via relational
query). So there is a challenge for all you boffins!!!
 
So for the moment, I am sticking to my own parent-child gridview methods -
discussed in this wiki. But, I am changing all my gridviews
to TbExtendedGridView, so that I could use all the other goodies.

But since TbExtendedGridView allows more events to update the parent-grid and
its columns, you might now need more control over what events should also update
the child-grid. So instead of clicking any place on the parent-row, I now use a
special button in the parent-row that updates the child-grid.

The button sends the parentID directly to actionAdmin in our controller, without
using our own custom ajax any more. So you can remove the section at the bottom
of the parentView, which loaded our own custom ajax function.


~~~
[php]
$this->widget('zii.widgets.grid.CGridView', array(   
 OR   
$this->widget('bootstrap.widgets.TbExtendedGridView', array(
	'ajaxUpdate' => 'childView', //or 'ajaxUpdate'=>'child-grid' /*keep this
line*/
	...
	'afterAjaxUpdate' => "updateChild", /*Remove this line*/
	'selectionChanged'=>"updateChild", /*Remove this line*/
	...
	array(
		'class'=>'CButtonColumn',
		'template'=>'{view} {update} {children}', /*Important: Add the children
			button to the template.*/
		'buttons'=>array(
			'view'=>array(
				...
			),
			'update'=>array(
				...
			),
			'children' => array(
				'label'=>'View Related Records',
				'url'=>'$this->grid->controller->createUrl("admin",
array(
					"parentID"=>$data->primaryKey,
				))',
				'options' => array(
					'ajax' => array(
						'type' => 'get',
						'url'=>'js:$(this).attr("href")',
						'success' => 'function(response){
							jQuery("#childDiv").html(response);
							/* you may add additional javascript statements
					 		here - such as making childDiv visible etc. */
						}',
					),
				),
			),
		),
	),


~~~

**********************************************************************************
**********************************************************************************
### Records and models
I often talk about records instead of models or model instances – but I think
you get the idea.
For those who do not know it yet (like myself, when I switched to OOP) the
differences between records and models are:

a record is a single row of data in a database table;

a model consists of many things such as: 

1. the record;

2. rules to be applied to each record;

3. rules for filtering records;

4. custom naming of fields in the record;

5. relations with other models;

6. your own custom functions;

7. arrays of data that you want to use in your code;

8. anything else you want to add – maybe sql, etc.;

**********************************************************************************
**********************************************************************************
Another use case: Child-grid in create and update views
-------------------------------------------------------

### Overview

I put the parent and child gridviews in the 'admin' view, but the following use
case of the 'create' and 'update' views, will allow you to add/delete
permissions to roles by adding/deleting records directly in the junction table.

In the Admin view, the user clicks on an update button of the role-grid, which
displays the update view for that role.

At the top of the update view, you have the role’s data, as normal.

Below that, you have a child gridview, displaying the permissions linked to the
above role.

Give the child gridview delete buttons that use the RolePermissionController to
delete the records from the junction table.
(The child gridview is only displayed when parent records are updated - not when
they are created.)

Below the child gridview, add a dropDownList where the user can select new
permissions (using child_models or maybe the Permission model directly) to be
linked to the role (new records are added to the junction table in the
RoleController).

Be careful:
Be very careful when deleting records. If your database is using cascading to
ensure referential integrity, you might be deleting records from other tables
without even knowing it. So rather just flag your records as being deleted (and
then scope them out with "default scope" or something) or at least
test to make sure the records have not been referenced in other tables. 

Although this is not a pure "dynamic gridviews" scenario, it is very
handy.

<a href="http://www.flickr.com/photos/77396592@N06/7329393188/"
title="CreateUpdate by Gerhard Liebenberg, on Flickr"><img
src="http://farm8.staticflickr.com/7091/7329393188_d24db5b374_b.jpg"
width="586" height="668"
alt="CreateUpdate"></a>

### The RoleController
~~~
[php]

/**
 * Creates a new model.
 * If creation is successful, the browser will be redirected to the 'view' page.
 */
public function actionCreate()
{
	$parent_model=new Role;
	$parentID = 0;

	// Uncomment the following line if AJAX validation is needed
	// $this->performAjaxValidation($parent_model);
	
	/* Create a single child-model instance which will hold the child-grid's
	filtering parameters entered by the user (not the gridview's data records).
	Put the	To create this child-model instance,
inuse the custom
	searchIncludingPermissions function of the
searchIncludingPermissions scenario.RolePermission model,
passing it
	the parentID. */
	$child_model = new
RolePermission("searchIncludingPermissions");RolePermission("searchIncludingPermissions($parentID)");
		
	/* Empty the newly created child-model instance to clear all parameters.*/
	$child_model->unsetAttributes();
		
	/*Put the child-model instance in the searchIncludingPermissions scenario
	to activate the model's safe rule when using the searchIncludingPermissions
	function. See the RolePermission model (in the Model method) for more 
	details on this scenario. */
	$child_model->scenario = 'searchIncludingPermissions';
		
	/*Test if the event currently using this action passed it any data to save*/
	if(isset($_POST['Role']))
	{
		$parent_model->attributes=$_POST['Role'];
			
		if($parent_model->save())/* Save the Role model */
		{
			/*The new role_id (auto increment) is only available after
			 the parent record was saved. It is needed to create the
			 child records. */
			$parentID = $parent_model->role_id;
				
			/*Test if the dropDownList, which uses a child_model
			 (RolePermission), passed any data in its permission_id
			 array */
			if(($_POST['RolePermission']['permission_id'])<>'')
			{
				foreach ($_POST['RolePermission']['permission_id']
				as $permissionId) {
					$this->linkChildRecord($parentID, $permissionId);
				}
			}
				
			/*Redirect to actionUpdate, because if you stay on the
			 create view a duplicate record would be created if the 
			user clicks the "Save" button */
			$this->redirect(array('update','id'=>$parentID));
		}
	}

	/*Render the create view - passing it all the filtering data it might need*/
	$this->render('create',array(
		'parent_model'=>$parent_model,
		'child_model'=>$child_model,
		'parentID' => $parentID
	));
}

/**
 * Updates a particular model.
 * If update is successful, the browser will be redirected to the 'view' page.
 * @param integer $id the ID of the model to be updated
 */
public function actionUpdate($id)
{
	$parent_model=$this->loadModel($id);
	$parentID = $id;
		
	// Uncomment the following line if AJAX validation is needed
	// $this->performAjaxValidation($parent_model);

	/*Test if the event currently using this action passed it any data to save*/
	if(isset($_POST['Role']))
	{
		$parent_model->attributes=$_POST['Role'];
		if($parent_model->save())/* Save the Role model */
		{
			/*Test if the dropDownList, which uses a child_model
			 (RolePermission), passed any data in its permission_id
			 array */
			if(($_POST['RolePermission']['permission_id'])<>'')
			{
				foreach ($_POST['RolePermission']['permission_id']
				as $permissionId) {
					$this->linkChildRecord($parentID, $permissionId);
				}
			}
			
			/* Here I choose to stay on the update view and not to
			 redirect*/
			/*$this->redirect(array('view','id'=>$parent_model->
			role_id));*/
		}
	}

	/* Create a single child filtering-modelchild-model
instance  */which will hold the child-grid's
	filtering parameters entered by the user (not the gridview's data records).
	To create this child-model instance, use the custom 
	searchIncludingPermissions function of the RolePermission model, passing it 
	the parentID. */
	$child_model = new
RolePermission("searchIncludingPermissions");RolePermission("searchIncludingPermissions($parentID)");
		
	/* Empty the newly created child-model instance to clear all parameters.*/
	$child_model->unsetAttributes();
		
	/*Put the child-model instance in the searchIncludingPermissions scenario
	 to activate the model's safe rule for the searchIncludingPermissions 
	function. See the RolePermission model for more details on this scenario. */
	$child_model->scenario = 'searchIncludingPermissions';
		
	/* Test if the event that is currently calling this action, passed any
	filtering parameters that the user might have entered in the child-grid.
	If true, store these parameters in the newly created child-model instance.*/
	if(isset($_GET['RolePermission']))
		$child_model->attributes=$_GET['RolePermission'];
		
	/*Render the update view - passing it all the filtering data it might need*/
	$this->render('update',array(
		'parent_model'=>$parent_model,
		'child_model'=>$child_model,
		'parentID' => $parentID
	));
}

/*This function is used by both the create and update actions, to create the 
records in the junction table */
private function linkChildRecord($parentID, $permissionId)
{
try { 
	/*Test if a RolePermission record with this "role_id ($parentID) &
	 permission_id"	combination already exists*/
		
	/* I used injection safe DAO sql, because it is faster than
	ActiveRecord and here we don't need all the model functionality that 
	ActiveRecord provides */
	$sql=
	"SELECT	cap_role_permission.rolepermission_id
	 FROM cap_role_permission
	 WHERE
		cap_role_permission.role_id=:varRoleId and
		cap_role_permission.permission_id=:varPermissionId";
			 
	$connection=Yii::app()->db;
	$command=$connection->createCommand($sql);
	$command->bindValue(':varRoleId',$parentID);
	$command->bindValue(':varPermissionId',$permissionId);
	$row=$command->queryRow();
	If ($row <> ""){
		/* Record already exists in RolePermission. Take no action or let
		 the user know. */
	}
	else{ /* Insert the new RolePermission record. */
		try{ 
			$rolePermission = new RolePermission;
			$rolePermission->role_id = $parentID;
			$rolePermission->permission_id = $permissionId;
			$rolePermission->save();
		}
		catch(Exception $e){
			echo($e);
		}
	}
			
}
catch(Exception $e) 
{
	echo($e);/* an exception is raised if ANY of the sql statements fails */
}
}

/*If you have lots of validation rules for your junction table
(role_permission), then it is better to use ActiveRecord. The above function
could look like this: */
private function linkChildRecord($parentID, $permissionId)
{
	$model=new RolePermission;
	$model->role_id =  $parentID;
	$model->permission_id =  $permissionId;
	$model->save();
}
~~~

### The views

views/role/create.php
~~~
[php]

<h1>Create Role</h1>

<?php
	echo $this->renderPartial('_form', array(
	'parent_model'=>$parent_model,
	'child_model' => $child_model,
	'parentID' => $parentID,
	));
?>
~~~

views/role/update.php
~~~
[php]

<h1>Update Role <?php echo $parent_model->role_id; ?></h1>

<?php
	echo $this->renderPartial('_form', array(
	'parent_model'=>$parent_model,
	'child_model' => $child_model,
	'parentID' => $parentID,
	));
?>
~~~

views/role/_form.php is used by both create.php and update.php.

~~~
[php]

<div class="form">
	
	<?php $form=$this->beginWidget('CActiveForm', array(
			'id'=>'role-form',
			'enableAjaxValidation'=>false,
		)); ?>
	
		<div class="solid_border">
			<p class="subsectionheading1">
				<?php
					If(!$parent_model->isNewRecord){					
						echo ("Data fields for Role " . $parentID );
					}
					else{
						echo ("Data fields for new Role");
					}
				?>
			</p>
			
			</br>
			
			<p class="note">Fields with <span
class="required">*</span>
			are required.</p>

			<?php echo $form->errorSummary($parent_model); ?>

			<div class="row">
				<?php echo $form->labelEx($parent_model,'role_desc'); ?>
				<?php echo $form->textField($parent_model,'role_desc',array
				('size'=>60,'maxlength'=>64)); ?>
				<?php echo $form->error($parent_model,'role_desc'); ?>
			</div>

		</div></br>
		
		<!-- Use PHP if-statement that allows HTML in result -->
		<?php if (!$parent_model->isNewRecord) : ?>
			<div id="childgrid" class="solid_border">
				<p class="subsectionheading1">Role-Permissions currently
linked
				to Role <?php echo $parentID ?></p>
				<?php
					$this->widget('zii.widgets.grid.CGridView', array(
						'id'=>'child-grid',
						'dataProvider'=>$child_model->searchIncludingPermissions
						($parentID),
						'filter'=>$child_model,
						'columns'=>array(
							'permission_id',
							array(
								'name'=>'permission_desc_param',
								'value'=>'($data->relPermission)?$data->
								relPermission->permission_desc:""', 
								'header'=>'Permission Description',
								'filter' => CHtml::activeTextField($child_model,
								'permission_desc_param'),
							),
							array(
								'class'=>'CButtonColumn',
								'template'=>'{delete}',
								'deleteButtonUrl' => 'array
								("rolepermission/delete", "id"=>$data->
								rolepermission_id)',
								'deleteButtonLabel' => 'Delete Link',
								'deleteButtonImageUrl' => Yii::app()->request->
								baseUrl.'/images/css/gridview/delink.png',
								'deleteConfirmation' => 
								"Are you sure you want to detach this Permission
								from the Role?\n\n (Neither the Permission nor
								the Role will be deleted. Only the link between
								them (RolePermission) will be deleted.)", 
							),
						),
					));
				?>
			</div></br>
		<?php endif; ?>
			
		<div class="solid_border">
			<p class="subsectionheading1">
				<?php
					If(!$parent_model->isNewRecord){
						echo ("Permissions that can be linked to Role " .
							 $parentID );
					}
					else{
						echo ("Permissions that can be linked to the new Role ");
					}
				?>
			</p>
			<div class="textaligncenter">
				</br>
				<?php
					$listData = CHtml::listData(Permission::model()->findAll(),
							'permission_id', 'permission_desc'); 
					
					asort($listData); /* sort dropDownList data */
		 
					echo $form->dropDownList($child_model,'permission_id',
						$listData,
						array(
							'id'=>'newPermissions',
							'multiple' => 'multiple',
							'size'=>'6')				
						);
				?>
							
				<?php echo $form->error($child_model,'permission_id'); ?>
			</div>
		</div>

		</br>
		
		<!-- Display the submit button on the BottomBar -->
		<div id="shortBottomBar"> 
			<?php echo CHtml::submitButton($parent_model->isNewRecord ?
				 'Create' : 'Save'); ?>
		</div>
		
	<!-- The dropDownList must be included BEFORE this endWidget() function,
	 otherwise its selected rows will not be submitted to the controller -->
	<?php $this->endWidget(); ?>
	
</div><!-- form -->
~~~
### Fix the submit button to the bottom of the screen

If you also want to fix your submit button to the bar at the bottom of the
screen you need to add a longBottomBar, which is displayed permanently. The
button is displayed with a shortBottomBar, which is rendered on top of the
longBottomBar.

I like this feature a lot, because the button is always visible. So the user
don't need to scroll down in order to submit a long form.

css/main.css:
~~~
[php]

div#longBottomBar
 {
	position:fixed;
	bottom:0;
	display: inline;  /* display direction inline */
	padding: 3px;
	width: 100%;
	background-color: #141414;
	height:28px;
	text-align: center;
	z-index: 10;       /* Z-index = 10. Move to back. */
 }
 @media screen
 {
body>div#longBottomBar{position: fixed;}
 }

div#shortBottomBar 
 {
	position:fixed;
	bottom:0;
	display: inline;
	padding: 3px;
	width: 565px;
	background-color: #141414;
	height:28px;
	text-align: center;
	z-index: 15;   /* Z-index = 15. Move in front of longBottomBar. */
 }
 @media screen
 {
body>div#shortBottomBar{position: fixed;}
 }
~~~

in views/layouts/main.php:
~~~
[php]

<head>
	...	
</head>

<body>
	...
	
	<div id="longBottomBar">	
	</div>
</body>
~~~

**********************************************************************************
Any suggestions for corrections and further improvements are welcome.

Thank you for your inputs softark and Haensel.

Gerhard