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Components

Components are packages of logic that are shared between controllers. CakePHP comes with a fantastic set of core components you can use to aid in various common tasks. You can also create your own components. If you find yourself wanting to copy and paste things between controllers, you should consider creating your own component to contain the functionality. Creating components keeps controller code clean and allows you to reuse code between projects.

Each of the core components is detailed in its own chapter. See Components. This section describes how to configure and use components, and how to create your own components.

Configuring Components

Many of the core components require configuration. Some examples of components requiring configuration are Authentication and Cookie. Configuration for these components, and for components in general, is usually done in the $components array or your controller’s beforeFilter() method:

class PostsController extends AppController {
    public $components = array(
        'Auth' => array(
            'authorize' => array('controller'),
            'loginAction' => array(
                'controller' => 'users',
                'action' => 'login'
            )
        ),
        'Cookie' => array('name' => 'CookieMonster')
    );

The previous fragment of code would be an example of configuring a component with the $components array. All core components allow their configuration settings to be set in this way. In addition, you can configure components in your controller’s beforeFilter() method. This is useful when you need to assign the results of a function to a component property. The above could also be expressed as:

public function beforeFilter() {
    $this->Auth->authorize = array('controller');
    $this->Auth->loginAction = array(
        'controller' => 'users',
        'action' => 'login'
    );

    $this->Cookie->name = 'CookieMonster';
}

It’s possible, however, that a component requires certain configuration options to be set before the controller’s beforeFilter() is run. To this end, some components allow configuration options be set in the $components array:

public $components = array(
    'DebugKit.Toolbar' => array('panels' => array('history', 'session'))
);

Consult the relevant documentation to determine what configuration options each component provides.

One common setting to use is the className option, which allows you to alias components. This feature is useful when you want to replace $this->Auth or another common Component reference with a custom implementation:

// app/Controller/PostsController.php
class PostsController extends AppController {
    public $components = array(
        'Auth' => array(
            'className' => 'MyAuth'
        )
    );
}

// app/Controller/Component/MyAuthComponent.php
App::uses('AuthComponent', 'Controller/Component');
class MyAuthComponent extends AuthComponent {
    // Add your code to override the core AuthComponent
}

The above would alias MyAuthComponent to $this->Auth in your controllers.

Note

Aliasing a component replaces that instance anywhere that component is used, including inside other Components.

Using Components

Once you’ve included some components in your controller, using them is pretty simple. Each component you use is exposed as a property on your controller. If you had loaded up the SessionComponent and the CookieComponent in your controller, you could access them like so:

class PostsController extends AppController {
    public $components = array('Session', 'Cookie');

    public function delete() {
        if ($this->Post->delete($this->request->data('Post.id')) {
            $this->Session->setFlash('Post deleted.');
            return $this->redirect(array('action' => 'index'));
        }
    }

Note

Since both Models and Components are added to Controllers as properties they share the same ‘namespace’. Be sure to not give a component and a model the same name.

Loading components on the fly

You might not need all of your components available on every controller action. In situations like this you can load a component at runtime using the Component Collection. From inside a controller’s method you can do the following:

$this->OneTimer = $this->Components->load('OneTimer');
$this->OneTimer->getTime();

Note

Keep in mind that loading a component on the fly will not call its initialize method. If the component you are calling has this method you will need to call it manually after load.

Component Callbacks

Components also offer a few request life-cycle callbacks that allow them to augment the request cycle. See the base Component API for more information on the callbacks components offer.

Creating a Component

Suppose our online application needs to perform a complex mathematical operation in many different parts of the application. We could create a component to house this shared logic for use in many different controllers.

The first step is to create a new component file and class. Create the file in app/Controller/Component/MathComponent.php. The basic structure for the component would look something like this:

App::uses('Component', 'Controller');
class MathComponent extends Component {
    public function doComplexOperation($amount1, $amount2) {
        return $amount1 + $amount2;
    }
}

Note

All components must extend Component. Failing to do this will trigger an exception.

Including your component in your controllers

Once our component is finished, we can use it in the application’s controllers by placing the component’s name (without the “Component” part) in the controller’s $components array. The controller will automatically be given a new attribute named after the component, through which we can access an instance of it:

/* Make the new component available at $this->Math,
as well as the standard $this->Session */
public $components = array('Math', 'Session');

Components declared in AppController will be merged with those in your other controllers. So there is no need to re-declare the same component twice.

When including Components in a Controller you can also declare a set of parameters that will be passed on to the Component’s constructor. These parameters can then be handled by the Component:

public $components = array(
    'Math' => array(
        'precision' => 2,
        'randomGenerator' => 'srand'
    ),
    'Session', 'Auth'
);

The above would pass the array containing precision and randomGenerator to MathComponent::__construct() as the second parameter. By convention, if array keys match component’s public properties, the properties will be set to the values of these keys.

Using other Components in your Component

Sometimes one of your components may need to use another component. In this case you can include other components in your component the exact same way you include them in controllers - using the $components var:

// app/Controller/Component/CustomComponent.php
App::uses('Component', 'Controller');
class CustomComponent extends Component {
    // the other component your component uses
    public $components = array('Existing');

    public function initialize(Controller $controller) {
        $this->Existing->foo();
    }

    public function bar() {
        // ...
   }
}

// app/Controller/Component/ExistingComponent.php
App::uses('Component', 'Controller');
class ExistingComponent extends Component {

    public function foo() {
        // ...
    }
}

Note

In contrast to a component included in a controller no callbacks will be triggered on a component’s component.

Component API

class Component

The base Component class offers a few methods for lazily loading other Components through ComponentCollection as well as dealing with common handling of settings. It also provides prototypes for all the component callbacks.

Component::__construct(ComponentCollection $collection, $settings = array())

Constructor for the base component class. All $settings that are also public properties will have their values changed to the matching value in $settings.

Callbacks

Component::initialize(Controller $controller)

Is called before the controller’s beforeFilter method.

Component::startup(Controller $controller)

Is called after the controller’s beforeFilter method but before the controller executes the current action handler.

Component::beforeRender(Controller $controller)

Is called after the controller executes the requested action’s logic, but before the controller’s renders views and layout.

Component::shutdown(Controller $controller)

Is called before output is sent to the browser.

Component::beforeRedirect(Controller $controller, $url, $status=null, $exit=true)

Is invoked when the controller’s redirect method is called but before any further action. If this method returns false the controller will not continue on to redirect the request. The $url, $status and $exit variables have same meaning as for the controller’s method. You can also return a string which will be interpreted as the URL to redirect to or return an associative array with the key ‘url’ and optionally ‘status’ and ‘exit’.