Yii 1.1: How to write a simple application component


Application component

An application component is a confortable way for share information among all component of the application

In Yii there are many application components, for example Yii::app()->db.

Creating the class

Let's imagine we need almost everywhere an instance of the class Region, and we want to avoid to do too much queries.

We can create a class which extends CApplicationComponent, like that:

class RegionSingleton extends CApplicationComponent
    private $_model=null;
    public function setModel($id)
    public function getModel()
        if (!$this->_model)
            if (isset($_GET['region']))
                $this->_model=Region::model()->findByAttributes(array('url_name'=> $_GET['region']));
        return $this->_model;
    public function getId()
        return $this->model->id;
    public function getName()
        return $this->model->name;

And include this class in config main:



Now, wherever in the application we can call


for have the model, or also


for retrive the id.

We can also set the model by using



This approach can be very useful and resource-saving, because we do at most only a single query.

Total 5 comments

#15001 report it
Maxx Astral at 2013/09/27 12:50pm
Registry pattern

As far as i know Registry Pattern is much like a key/value storage. Much like an object library. It can be used to retrieve same instance of an object as well as create and remove other instances. And it has global scope. So in a way it overcomes the single instance limitation of Singleton, as it allows us to have multiple instances available at any point of time.

#8408 report it
ianaré at 2012/05/31 07:48pm
De Facto Singleton

Since there can be only one instance of an application component per CWebApplication, it acts like a singleton, even if not stored in a static property.

#3889 report it
_wk_ at 2011/05/17 07:21pm
Not Registry either

I don't believe this is the Registry pattern either. To my knowledge a Registry pattern is form of singleton that controls storage of values inside it. A value can be set but not unset. See the Zend_Registry component as a reference.

#3888 report it
_wk_ at 2011/05/17 07:17pm
Incorrect pattern

A singleton will have a protected or private constructor with a static method that will return a single instance of the object. This is limits to one object being created hence the name 'Singleton'.

#3769 report it
mitallast at 2011/05/06 07:33am
It is not singleton

It is not singleton. This pattern name is Registry, using for dependency injection in your application.

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