Controllers

After creating the resource classes and specifying how resource data should be formatted, the next thing to do is to create controller actions to expose the resources to end users through RESTful APIs.

Yii provides two base controller classes to simplify your work of creating RESTful actions: yii\rest\Controller and yii\rest\ActiveController. The difference between these two controllers is that the latter provides a default set of actions that are specifically designed to deal with resources represented as Active Record. So if you are using Active Record and are comfortable with the provided built-in actions, you may consider extending your controller classes from yii\rest\ActiveController, which will allow you to create powerful RESTful APIs with minimal code.

Both yii\rest\Controller and yii\rest\ActiveController provide the following features, some of which will be described in detail in the next few sections:

HTTP method validation;
Content negotiation and Data formatting;
Authentication;
Rate limiting.

yii\rest\ActiveController in addition provides the following features:

A set of commonly needed actions: index, view, create, update, delete, options;
User authorization in regarding to the requested action and resource.

Creating Controller Classes

When creating a new controller class, a convention in naming the controller class is to use the type name of the resource and use singular form. For example, to serve user information, the controller may be named as UserController.

Creating a new action is similar to creating an action for a Web application. The only difference is that instead of rendering the result using a view by calling the render() method, for RESTful actions you directly return the data. The yii\rest\Controller::serializer and the yii\web\Response will handle the conversion from the original data to the requested format. For example,

public function actionView($id)
{
    return User::findOne($id);
}

Filters

Most RESTful API features provided by yii\rest\Controller are implemented in terms of filters. In particular, the following filters will be executed in the order they are listed:

yii\filters\ContentNegotiator: supports content negotiation, to be explained in the Response Formatting section;
yii\filters\VerbFilter: supports HTTP method validation;
yii\filters\AuthMethod: supports user authentication, to be explained in the Authentication section;
yii\filters\RateLimiter: supports rate limiting, to be explained in the Rate Limiting section.

These named filters are declared in the yii\rest\Controller::behaviors() method. You may override this method to configure individual filters, disable some of them, or add your own filters. For example, if you only want to use HTTP basic authentication, you may write the following code:

use yii\filters\auth\HttpBasicAuth;

public function behaviors()
{
    $behaviors = parent::behaviors();
    $behaviors['authenticator'] = [
        'class' => HttpBasicAuth::className(),
    ];
    return $behaviors;
}

Extending `ActiveController`

If your controller class extends from yii\rest\ActiveController, you should set its yii\rest\ActiveController::modelClass property to be the name of the resource class that you plan to serve through this controller. The class must extend from yii\db\ActiveRecord.

Customizing Actions

By default, yii\rest\ActiveController provides the following actions:

yii\rest\IndexAction: list resources page by page;
yii\rest\ViewAction: return the details of a specified resource;
yii\rest\CreateAction: create a new resource;
yii\rest\UpdateAction: update an existing resource;
yii\rest\DeleteAction: delete the specified resource;
yii\rest\OptionsAction: return the supported HTTP methods.

All these actions are declared through the yii\rest\ActiveController::actions() method. You may configure these actions or disable some of them by overriding the actions() method, like shown the following,

public function actions()
{
    $actions = parent::actions();

    // disable the "delete" and "create" actions
    unset($actions['delete'], $actions['create']);

    // customize the data provider preparation with the "prepareDataProvider()" method
    $actions['index']['prepareDataProvider'] = [$this, 'prepareDataProvider'];

    return $actions;
}

public function prepareDataProvider()
{
    // prepare and return a data provider for the "index" action
}

Please refer to the class references for individual action classes to learn what configuration options are available.

Performing Access Check

When exposing resources through RESTful APIs, you often need to check if the current user has the permission to access and manipulate the requested resource(s). With yii\rest\ActiveController, this can be done by overriding the yii\rest\ActiveController::checkAccess() method like the following,

/**
 * Checks the privilege of the current user.
 *
 * This method should be overridden to check whether the current user has the privilege
 * to run the specified action against the specified data model.
 * If the user does not have access, a [[ForbiddenHttpException]] should be thrown.
 *
 * @param string $action the ID of the action to be executed
 * @param \yii\base\Model $model the model to be accessed. If null, it means no specific model is being accessed.
 * @param array $params additional parameters
 * @throws ForbiddenHttpException if the user does not have access
 */
public function checkAccess($action, $model = null, $params = [])
{
    // check if the user can access $action and $model
    // throw ForbiddenHttpException if access should be denied
}

The checkAccess() method will be called by the default actions of yii\rest\ActiveController. If you create new actions and also want to perform access check, you should call this method explicitly in the new actions.

Tip: You may implement checkAccess() by using the Role-Based Access Control (RBAC) component.

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