View

A view is a PHP script consisting of mainly elements of user interface. It can contain PHP statements, but it is recommended that these statements should not alter data models and should remain relatively simple. For the spirit of separation of logic and presentation, large chunk of logic should be placed in controller or model instead of view.

A view has a name which is used to identify the view script file when rendering. The name of a view is the same as the name of its view script file. For example, view edit refers to a view script file named as edit.php. To render a view, call CController::render() with the name of the view. The method will look for the corresponding view file under the directory protected/views/ControllerID.

Inside the view script, we can access the controller instance using $this. We can thus pull in any property of the controller by evaluating $this->propertyName in the view.

We can also use the following push approach to pass data to the view:

$this->render('edit', array(
    'var1'=>$value1,
    'var2'=>$value2,
));

In the above, the render() method will extract the second array parameter into variables. As a result, in the view script we can access local variables $var1 and $var2.

1. Layout

Layout is a special view that is used to decorate views. It usually contains portions of user interface that are common among several views. For example, a layout may contain header and footer portions and embed the content view in between,

......header here......
<?php echo $content; ?>
......footer here......

where $content stores the rendering result of the content view.

Layout is implicitly applied when calling render(). By default, the view script protected/views/layouts/main.php is used as the layout. This can be customized by changing either CWebApplication::layout or CController::layout. To render a view without applying any layout, call renderPartial() instead.

2. Widget

A widget is an instance of CWidget or its child class. It is a component mainly for presentational purpose. Widgets are usually embedded in a view script to generate some complex yet self-contained user interface. For example, a calendar widget can be used to render a complex calendar user interface. Widgets enable better reusability in user interface.

To use a widget, do as follows in a view script:

<?php $this->beginWidget('path.to.WidgetClass'); ?>
...body content that may be captured by the widget...
<?php $this->endWidget(); ?>

or

<?php $this->widget('path.to.WidgetClass'); ?>

The latter is used when the widget does not need any body content.

Widgets can be configured to customize its behaviors. This is done by settings their initial property values when calling CBaseController::beginWidget or CBaseController::widget. For example, when using CMaskedTextField widget, we would like to specify the mask being used. We can do so by passing an array of those property initial values as follows, where the array keys are property names and array values the initial values of the corresponding widget properties:

<?php
$this->widget('CMaskedTextField',array(
    'mask'=>'99/99/9999'
));
?>

To define a new widget, extend CWidget and override its init() and run() methods:

class MyWidget extends CWidget
{
    public function init()
    {
        // this method is called by CController::beginWidget()
    }
 
    public function run()
    {
        // this method is called by CController::endWidget()
    }
}

Like a controller, a widget can also have its own view. By default, widget view files are located under the views subdirectory of the directory containing the widget class file. These views can be rendered by calling CWidget::render(), similar to that in controller. The only difference is that no layout will be applied to a widget view.

3. System View

System views refer to the views used by Yii to display error and logging information. For example, when a user requests for a non-existing controller or action, Yii will throw an exception explaining the error. Yii displays the exception using a specific system view.

The naming of system views follows some rules. Names like errorXXX refer to views for displaying CHttpException with error code XXX. For example, if CHttpException is raised with error code 404, the error404 view will be displayed.

Yii provides a set of default system views located under framework/views. They can be customized by creating the same-named view files under protected/views/system.

$Id: basics.view.txt 409 2008-12-26 02:55:09Z qiang.xue $

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