# Class yii\di\Container

Inheritance | yii\di\Container » yii\base\Component » yii\base\BaseObject
Implements | yii\base\Configurable
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/di/Container.php

Container implements a dependency injection container.

A dependency injection (DI) container is an object that knows how to instantiate and configure objects and all their dependent objects. For more information about DI, please refer to Martin Fowler's article.

Container supports constructor injection as well as property injection.

To use Container, you first need to set up the class dependencies by calling set(). You then call get() to create a new class object. Container will automatically instantiate dependent objects, inject them into the object being created, configure and finally return the newly created object.

By default, Yii::$container refers to a Container instance which is used by Yii::createObject() to create new object instances. You may use this method to replace the `new` operator when creating a new object, which gives you the benefit of automatic dependency resolution and default property configuration.

Below is an example of using Container:

    namespace app\models;

    use yii\base\BaseObject;
    use yii\db\Connection;
    use yii\di\Container;

    interface UserFinderInterface
    {
        function findUser();
    }

    class UserFinder extends BaseObject implements UserFinderInterface
    {
        public $db;

        public function __construct(Connection $db, $config = [])
        {
            $this->db = $db;
            parent::__construct($config);
        }

        public function findUser()
        {
        }
    }

    class UserLister extends BaseObject
    {
        public $finder;

        public function __construct(UserFinderInterface $finder, $config = [])
        {
            $this->finder = $finder;
            parent::__construct($config);
        }
    }

    $container = new Container;
    $container->set('yii\db\Connection', [
        'dsn' => '...',
    ]);
    $container->set('app\models\UserFinderInterface', [
        'class' => 'app\models\UserFinder',
    ]);
    $container->set('userLister', 'app\models\UserLister');

    $lister = $container->get('userLister');

    // which is equivalent to:

    $db = new \yii\db\Connection(['dsn' => '...']);
    $finder = new UserFinder($db);
    $lister = new UserLister($finder);

For more details and usage information on Container, see the guide article on di-containers.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$behaviors | yii\base\Behavior[] | List of behaviors attached to this component. This property is read-only. | yii\base\Component
$definitions | array | The list of the object definitions or the loaded shared objects (type or ID => definition or instance). This property is read-only. | yii\di\Container
$resolveArrays | boolean | Whether to attempt to resolve elements in array dependencies. This property is write-only. | yii\di\Container
$singleton | string | Class name, interface name or alias name | yii\di\Container
$singletons | array | Array of singleton definitions. | yii\di\Container

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\Component
__clone() | This method is called after the object is created by cloning an existing one. | yii\base\Component
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of a component property. | yii\base\Component
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\Component
__set() | Sets the value of a component property. | yii\base\Component
__unset() | Sets a component property to be null. | yii\base\Component
attachBehavior() | Attaches a behavior to this component. | yii\base\Component
attachBehaviors() | Attaches a list of behaviors to the component. | yii\base\Component
behaviors() | Returns a list of behaviors that this component should behave as. | yii\base\Component
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\Component
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\Component
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
clear() | Removes the definition for the specified name. | yii\di\Container
detachBehavior() | Detaches a behavior from the component. | yii\base\Component
detachBehaviors() | Detaches all behaviors from the component. | yii\base\Component
ensureBehaviors() | Makes sure that the behaviors declared in behaviors() are attached to this component. | yii\base\Component
get() | Returns an instance of the requested class. | yii\di\Container
getBehavior() | Returns the named behavior object. | yii\base\Component
getBehaviors() | Returns all behaviors attached to this component. | yii\base\Component
getDefinitions() | Returns the list of the object definitions or the loaded shared objects. | yii\di\Container
has() | Returns a value indicating whether the container has the definition of the specified name. | yii\di\Container
hasEventHandlers() | Returns a value indicating whether there is any handler attached to the named event. | yii\base\Component
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\Component
hasProperty() | Returns a value indicating whether a property is defined for this component. | yii\base\Component
hasSingleton() | Returns a value indicating whether the given name corresponds to a registered singleton. | yii\di\Container
init() | Initializes the object. | yii\base\BaseObject
invoke() | Invoke a callback with resolving dependencies in parameters. | yii\di\Container
off() | Detaches an existing event handler from this component. | yii\base\Component
on() | Attaches an event handler to an event. | yii\base\Component
resolveCallableDependencies() | Resolve dependencies for a function. | yii\di\Container
set() | Registers a class definition with this container. | yii\di\Container
setDefinitions() | Registers class definitions within this container. | yii\di\Container
setResolveArrays() |  | yii\di\Container
setSingleton() | Registers a class definition with this container and marks the class as a singleton class. | yii\di\Container
setSingletons() | Registers class definitions as singletons within this container by calling setSingleton(). | yii\di\Container
trigger() | Triggers an event. | yii\base\Component

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
build() | Creates an instance of the specified class. | yii\di\Container
getDependencies() | Returns the dependencies of the specified class. | yii\di\Container
mergeParams() | Merges the user-specified constructor parameters with the ones registered via set(). | yii\di\Container
normalizeDefinition() | Normalizes the class definition. | yii\di\Container
resolveDependencies() | Resolves dependencies by replacing them with the actual object instances. | yii\di\Container

## Property Details

$definitions public property

The list of the object definitions or the loaded shared objects (type or ID => definition or instance). This property is read-only.

public array $definitions = null
$resolveArrays public property

Whether to attempt to resolve elements in array dependencies. This property is write-only.

public boolean $resolveArrays = null
$singleton public write-only property

Class name, interface name or alias name

public $this setSingleton ( $class, $definition = [], array $params = [] )
$singletons public write-only property (available since version 2.0.11)

Array of singleton definitions. See setDefinitions() for allowed formats of array.

public void setSingletons ( array $singletons )

## Method Details

build() protected method

Creates an instance of the specified class.

This method will resolve dependencies of the specified class, instantiate them, and inject them into the new instance of the specified class.

protected object build ( $class, $params, $config )
$class | string | The class name
$params | array | Constructor parameters
$config | array | Configurations to be applied to the new instance
return | object | The newly created instance of the specified class
throws | yii\di\NotInstantiableException | If resolved to an abstract class or an interface (since 2.0.9)

clear() public method

Removes the definition for the specified name.

public void clear ( $class )
$class | string | Class name, interface name or alias name

get() public method

Returns an instance of the requested class.

You may provide constructor parameters (`$params`) and object configurations (`$config`) that will be used during the creation of the instance.

If the class implements yii\base\Configurable, the `$config` parameter will be passed as the last parameter to the class constructor; Otherwise, the configuration will be applied after the object is instantiated.

Note that if the class is declared to be singleton by calling setSingleton(), the same instance of the class will be returned each time this method is called. In this case, the constructor parameters and object configurations will be used only if the class is instantiated the first time.

public object get ( $class, $params = [], $config = [] )
$class | string|yii\di\Instance | The class Instance, name or an alias name (e.g. `foo`) that was previously registered via set() or setSingleton().
$params | array | A list of constructor parameter values. Use one of two definitions: Parameters as name-value pairs, for example: `['posts' => PostRepository::class]`. Parameters in the order they appear in the constructor declaration. If you want to skip some parameters, you should index the remaining ones with the integers that represent their positions in the constructor parameter list. Dependencies indexed by name and by position in the same array are not allowed.
$config | array | A list of name-value pairs that will be used to initialize the object properties.
return | object | An instance of the requested class.
throws | yii\base\InvalidConfigException | if the class cannot be recognized or correspond to an invalid definition
throws | yii\di\NotInstantiableException | If resolved to an abstract class or an interface (since 2.0.9)

getDefinitions() public method

Returns the list of the object definitions or the loaded shared objects.

public array getDefinitions ( )
return | array | The list of the object definitions or the loaded shared objects (type or ID => definition or instance).

getDependencies() protected method

Returns the dependencies of the specified class.

protected array getDependencies ( $class )
$class | string | Class name, interface name or alias name
return | array | The dependencies of the specified class.
throws | yii\di\NotInstantiableException | if a dependency cannot be resolved or if a dependency cannot be fulfilled.

has() public method

Returns a value indicating whether the container has the definition of the specified name.

See also set().

public boolean has ( $class )
$class | string | Class name, interface name or alias name
return | boolean | Whether the container has the definition of the specified name..

hasSingleton() public method

Returns a value indicating whether the given name corresponds to a registered singleton.

public boolean hasSingleton ( $class, $checkInstance = false )
$class | string | Class name, interface name or alias name
$checkInstance | boolean | Whether to check if the singleton has been instantiated.
return | boolean | Whether the given name corresponds to a registered singleton. If `$checkInstance` is true, the method should return a value indicating whether the singleton has been instantiated.

invoke() public method (available since version 2.0.7)

Invoke a callback with resolving dependencies in parameters.

This methods allows invoking a callback and let type hinted parameter names to be resolved as objects of the Container. It additionally allow calling function using named parameters.

For example, the following callback may be invoked using the Container to resolve the formatter dependency:

    $formatString = function($string, \yii\i18n\Formatter $formatter) {
       // ...
    }
    Yii::$container->invoke($formatString, ['string' => 'Hello World!']);

This will pass the string `'Hello World!'` as the first param, and a formatter instance created by the DI container as the second param to the callable.

public mixed invoke ( callable $callback, $params = [] )
$callback | callable | Callable to be invoked.
$params | array | The array of parameters for the function. This can be either a list of parameters, or an associative array representing named function parameters.
return | mixed | The callback return value.
throws | yii\base\InvalidConfigException | if a dependency cannot be resolved or if a dependency cannot be fulfilled.
throws | yii\di\NotInstantiableException | If resolved to an abstract class or an interface (since 2.0.9)

mergeParams() protected method

Merges the user-specified constructor parameters with the ones registered via set().

protected array mergeParams ( $class, $params )
$class | string | Class name, interface name or alias name
$params | array | The constructor parameters
return | array | The merged parameters

normalizeDefinition() protected method

Normalizes the class definition.

protected array normalizeDefinition ( $class, $definition )
$class | string | Class name
$definition | string|array|callable | The class definition
return | array | The normalized class definition
throws | yii\base\InvalidConfigException | if the definition is invalid.

resolveCallableDependencies() public method (available since version 2.0.7)

Resolve dependencies for a function.

This method can be used to implement similar functionality as provided by invoke() in other components.

public array resolveCallableDependencies ( callable $callback, $params = [] )
$callback | callable | Callable to be invoked.
$params | array | The array of parameters for the function, can be either numeric or associative.
return | array | The resolved dependencies.
throws | yii\base\InvalidConfigException | if a dependency cannot be resolved or if a dependency cannot be fulfilled.
throws | yii\di\NotInstantiableException | If resolved to an abstract class or an interface (since 2.0.9)

resolveDependencies() protected method

Resolves dependencies by replacing them with the actual object instances.

protected array resolveDependencies ( $dependencies, $reflection = null )
$dependencies | array | The dependencies
$reflection | ReflectionClass | The class reflection associated with the dependencies
return | array | The resolved dependencies
throws | yii\base\InvalidConfigException | if a dependency cannot be resolved or if a dependency cannot be fulfilled.

set() public method

Registers a class definition with this container.

For example,

    // register a class name as is. This can be skipped.
    $container->set('yii\db\Connection');

    // register an interface
    // When a class depends on the interface, the corresponding class
    // will be instantiated as the dependent object
    $container->set('yii\mail\MailInterface', 'yii\swiftmailer\Mailer');

    // register an alias name. You can use $container->get('foo')
    // to create an instance of Connection
    $container->set('foo', 'yii\db\Connection');

    // register a class with configuration. The configuration
    // will be applied when the class is instantiated by get()
    $container->set('yii\db\Connection', [
        'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
        'username' => 'root',
        'password' => '',
        'charset' => 'utf8',
    ]);

    // register an alias name with class configuration
    // In this case, a "class" element is required to specify the class
    $container->set('db', [
        'class' => 'yii\db\Connection',
        'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
        'username' => 'root',
        'password' => '',
        'charset' => 'utf8',
    ]);

    // register a PHP callable
    // The callable will be executed when $container->get('db') is called
    $container->set('db', function ($container, $params, $config) {
        return new \yii\db\Connection($config);
    });

If a class definition with the same name already exists, it will be overwritten with the new one. You may use has() to check if a class definition already exists.

public $this set ( $class, $definition = [], array $params = [] )
$class | string | Class name, interface name or alias name
$definition | mixed | The definition associated with `$class`. It can be one of the following: a PHP callable: The callable will be executed when get() is invoked. The signature of the callable should be `function ($container, $params, $config)`, where `$params` stands for the list of constructor parameters, `$config` the object configuration, and `$container` the container object. The return value of the callable will be returned by get() as the object instance requested. a configuration array: the array contains name-value pairs that will be used to initialize the property values of the newly created object when get() is called. The `class` element stands for the the class of the object to be created. If `class` is not specified, `$class` will be used as the class name. a string: a class name, an interface name or an alias name.
$params | array | The list of constructor parameters. The parameters will be passed to the class constructor when get() is called.
return | $this | The container itself

setDefinitions() public method (available since version 2.0.11)

Registers class definitions within this container.

See also set() to know more about possible values of definitions.

public void setDefinitions ( array $definitions )
$definitions | array | Array of definitions. There are two allowed formats of array. The first format: key: class name, interface name or alias name. The key will be passed to the set() method as a first argument `$class`. value: the definition associated with `$class`. Possible values are described in set() documentation for the `$definition` parameter. Will be passed to the set() method as the second argument `$definition`. Example: ```php $container->setDefinitions([
    'yii\web\Request' => 'app\components\Request',
    'yii\web\Response' => [
        'class' => 'app\components\Response',
        'format' => 'json'
    ],
    'foo\Bar' => function () {
        $qux = new Qux;
        $foo = new Foo($qux);
        return new Bar($foo);
    }
]); ``` The second format: key: class name, interface name or alias name. The key will be passed to the set() method as a first argument `$class`. value: array of two elements. The first element will be passed the set() method as the second argument `$definition`, the second one — as `$params`. Example: ```php $container->setDefinitions([
    'foo\Bar' => [
         ['class' => 'app\Bar'],
         [Instance::of('baz')]
     ]
]); ```

setResolveArrays() public method (available since version 2.0.37)

public void setResolveArrays ( $value )
$value | boolean | Whether to attempt to resolve elements in array dependencies

setSingleton() public method

Registers a class definition with this container and marks the class as a singleton class.

This method is similar to set() except that classes registered via this method will only have one instance. Each time get() is called, the same instance of the specified class will be returned.

See also set().

public $this setSingleton ( $class, $definition = [], array $params = [] )
$class | string | Class name, interface name or alias name
$definition | mixed | The definition associated with `$class`. See set() for more details.
$params | array | The list of constructor parameters. The parameters will be passed to the class constructor when get() is called.
return | $this | The container itself

setSingletons() public method (available since version 2.0.11)

Registers class definitions as singletons within this container by calling setSingleton().

See also:

- setDefinitions() for allowed formats of $singletons parameter.
- setSingleton() to know more about possible values of definitions.

public void setSingletons ( array $singletons )
$singletons | array | Array of singleton definitions. See setDefinitions() for allowed formats of array.