Class yii\base\Component
Component is the base class that implements the property, event and behavior features.
Component provides the event and behavior features, in addition to the property feature which is implemented in its parent class BaseObject.
Event is a way to "inject" custom code into existing code at certain places. For example, a comment object can trigger an "add" event when the user adds a comment. We can write custom code and attach it to this event so that when the event is triggered (i.e. comment will be added), our custom code will be executed.
An event is identified by a name that should be unique within the class it is defined at. Event names are case-sensitive.
One or multiple PHP callbacks, called event handlers, can be attached to an event. You can call trigger() to raise an event. When an event is raised, the event handlers will be invoked automatically in the order they were attached.
To attach an event handler to an event, call on():
$post->on('update', function ($event) {
// send email notification
});
In the above, an anonymous function is attached to the "update" event of the post. You may attach the following types of event handlers:
- anonymous function:
function ($event) { ... } - object method:
[$object, 'handleAdd'] - static class method:
['Page', 'handleAdd'] - global function:
'handleAdd'
The signature of an event handler should be like the following:
function foo($event)
where $event is an yii\base\Event object which includes parameters associated with the event.
You can also attach a handler to an event when configuring a component with a configuration array. The syntax is like the following:
[
'on add' => function ($event) { ... }
]
where on add stands for attaching an event to the add event.
Sometimes, you may want to associate extra data with an event handler when you attach it to an event and then access it when the handler is invoked. You may do so by
$post->on('update', function ($event) {
// the data can be accessed via $event->data
}, $data);
A behavior is an instance of yii\base\Behavior or its child class. A component can be attached with one or multiple behaviors. When a behavior is attached to a component, its public properties and methods can be accessed via the component directly, as if the component owns those properties and methods.
To attach a behavior to a component, declare it in behaviors(), or explicitly call attachBehavior(). Behaviors declared in behaviors() are automatically attached to the corresponding component.
One can also attach a behavior to a component when configuring it with a configuration array. The syntax is like the following:
[
'as tree' => [
'class' => 'Tree',
],
]
where as tree stands for attaching a behavior named tree, and the array will be passed to Yii::createObject()
to create the behavior object.
For more details and usage information on Component, see the guide article on components.
Public Properties
| Property | Type | Description | Defined By |
|---|---|---|---|
| $behaviors | yii\base\Behavior[] | List of behaviors attached to this component | yii\base\Component |
Public 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 |
| 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 |
| getBehavior() | Returns the named behavior object. | yii\base\Component |
| getBehaviors() | Returns all behaviors attached to this component. | yii\base\Component |
| 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 |
| init() | Initializes the object. | yii\base\BaseObject |
| off() | Detaches an existing event handler from this component. | yii\base\Component |
| on() | Attaches an event handler to an event. | yii\base\Component |
| trigger() | Triggers an event. | yii\base\Component |
Property Details
List of behaviors attached to this component
Method Details
Calls the named method which is not a class method.
This method will check if any attached behavior has the named method and will execute it if available.
Do not call this method directly as it is a PHP magic method that will be implicitly called when an unknown method is being invoked.
| public mixed __call ( $name, $params ) | ||
| $name | string | The method name |
| $params | array | Method parameters |
| return | mixed | The method return value |
|---|---|---|
| throws | yii\base\UnknownMethodException | when calling unknown method |
This method is called after the object is created by cloning an existing one.
It removes all behaviors because they are attached to the old object.
| public void __clone ( ) |
Returns the value of a component property.
This method will check in the following order and act accordingly:
- a property defined by a getter: return the getter result
- a property of a behavior: return the behavior property value
Do not call this method directly as it is a PHP magic method that
will be implicitly called when executing $value = $component->property;.
See also __set().
| public mixed __get ( $name ) | ||
| $name | string | The property name |
| return | mixed | The property value or the value of a behavior's property |
|---|---|---|
| throws | yii\base\UnknownPropertyException | if the property is not defined |
| throws | yii\base\InvalidCallException | if the property is write-only. |
Checks if a property is set, i.e. defined and not null.
This method will check in the following order and act accordingly:
- a property defined by a setter: return whether the property is set
- a property of a behavior: return whether the property is set
- return
falsefor non existing properties
Do not call this method directly as it is a PHP magic method that
will be implicitly called when executing isset($component->property).
| public boolean __isset ( $name ) | ||
| $name | string | The property name or the event name |
| return | boolean | Whether the named property is set |
|---|---|---|
Sets the value of a component property.
This method will check in the following order and act accordingly:
- a property defined by a setter: set the property value
- an event in the format of "on xyz": attach the handler to the event "xyz"
- a behavior in the format of "as xyz": attach the behavior named as "xyz"
- a property of a behavior: set the behavior property value
Do not call this method directly as it is a PHP magic method that
will be implicitly called when executing $component->property = $value;.
See also __get().
| public void __set ( $name, $value ) | ||
| $name | string | The property name or the event name |
| $value | mixed | The property value |
| throws | yii\base\UnknownPropertyException | if the property is not defined |
|---|---|---|
| throws | yii\base\InvalidCallException | if the property is read-only. |
Sets a component property to be null.
This method will check in the following order and act accordingly:
- a property defined by a setter: set the property value to be null
- a property of a behavior: set the property value to be null
Do not call this method directly as it is a PHP magic method that
will be implicitly called when executing unset($component->property).
| public void __unset ( $name ) | ||
| $name | string | The property name |
| throws | yii\base\InvalidCallException | if the property is read only. |
|---|---|---|
Attaches a behavior to this component.
This method will create the behavior object based on the given configuration. After that, the behavior object will be attached to this component by calling the yii\base\Behavior::attach() method.
See also detachBehavior().
| public yii\base\Behavior attachBehavior ( $name, $behavior ) | ||
| $name | string | The name of the behavior. |
| $behavior | string|array|yii\base\Behavior | The behavior configuration. This can be one of the following:
|
| return | yii\base\Behavior | The behavior object |
|---|---|---|
Attaches a list of behaviors to the component.
Each behavior is indexed by its name and should be a yii\base\Behavior object, a string specifying the behavior class, or an configuration array for creating the behavior.
See also attachBehavior().
| public void attachBehaviors ( $behaviors ) | ||
| $behaviors | array | List of behaviors to be attached to the component |
Returns a list of behaviors that this component should behave as.
Child classes may override this method to specify the behaviors they want to behave as.
The return value of this method should be an array of behavior objects or configurations indexed by behavior names. A behavior configuration can be either a string specifying the behavior class or an array of the following structure:
'behaviorName' => [
'class' => 'BehaviorClass',
'property1' => 'value1',
'property2' => 'value2',
]
Note that a behavior class must extend from yii\base\Behavior. Behaviors can be attached using a name or anonymously. When a name is used as the array key, using this name, the behavior can later be retrieved using getBehavior() or be detached using detachBehavior(). Anonymous behaviors can not be retrieved or detached.
Behaviors declared in this method will be attached to the component automatically (on demand).
| public array behaviors ( ) | ||
| return | array | The behavior configurations. |
|---|---|---|
Returns a value indicating whether a property can be read.
A property can be read if:
- the class has a getter method associated with the specified name (in this case, property name is case-insensitive);
- the class has a member variable with the specified name (when
$checkVarsis true); - an attached behavior has a readable property of the given name (when
$checkBehaviorsis true).
See also canSetProperty().
| public boolean canGetProperty ( $name, $checkVars = true, $checkBehaviors = true ) | ||
| $name | string | The property name |
| $checkVars | boolean | Whether to treat member variables as properties |
| $checkBehaviors | boolean | Whether to treat behaviors' properties as properties of this component |
| return | boolean | Whether the property can be read |
|---|---|---|
Returns a value indicating whether a property can be set.
A property can be written if:
- the class has a setter method associated with the specified name (in this case, property name is case-insensitive);
- the class has a member variable with the specified name (when
$checkVarsis true); - an attached behavior has a writable property of the given name (when
$checkBehaviorsis true).
See also canGetProperty().
| public boolean canSetProperty ( $name, $checkVars = true, $checkBehaviors = true ) | ||
| $name | string | The property name |
| $checkVars | boolean | Whether to treat member variables as properties |
| $checkBehaviors | boolean | Whether to treat behaviors' properties as properties of this component |
| return | boolean | Whether the property can be written |
|---|---|---|
Detaches a behavior from the component.
The behavior's yii\base\Behavior::detach() method will be invoked.
| public null|yii\base\Behavior detachBehavior ( $name ) | ||
| $name | string | The behavior's name. |
| return | null|yii\base\Behavior | The detached behavior. Null if the behavior does not exist. |
|---|---|---|
Detaches all behaviors from the component.
| public void detachBehaviors ( ) |
Makes sure that the behaviors declared in behaviors() are attached to this component.
| public void ensureBehaviors ( ) |
Returns the named behavior object.
| public null|yii\base\Behavior getBehavior ( $name ) | ||
| $name | string | The behavior name |
| return | null|yii\base\Behavior | The behavior object, or null if the behavior does not exist |
|---|---|---|
Returns all behaviors attached to this component.
| public yii\base\Behavior[] getBehaviors ( ) | ||
| return | yii\base\Behavior[] | List of behaviors attached to this component |
|---|---|---|
Returns a value indicating whether there is any handler attached to the named event.
| public boolean hasEventHandlers ( $name ) | ||
| $name | string | The event name |
| return | boolean | Whether there is any handler attached to the event. |
|---|---|---|
Returns a value indicating whether a method is defined.
A method is defined if:
- the class has a method with the specified name
- an attached behavior has a method with the given name (when
$checkBehaviorsis true).
| public boolean hasMethod ( $name, $checkBehaviors = true ) | ||
| $name | string | The property name |
| $checkBehaviors | boolean | Whether to treat behaviors' methods as methods of this component |
| return | boolean | Whether the method is defined |
|---|---|---|
Returns a value indicating whether a property is defined for this component.
A property is defined if:
- the class has a getter or setter method associated with the specified name (in this case, property name is case-insensitive);
- the class has a member variable with the specified name (when
$checkVarsis true); - an attached behavior has a property of the given name (when
$checkBehaviorsis true).
See also:
| public boolean hasProperty ( $name, $checkVars = true, $checkBehaviors = true ) | ||
| $name | string | The property name |
| $checkVars | boolean | Whether to treat member variables as properties |
| $checkBehaviors | boolean | Whether to treat behaviors' properties as properties of this component |
| return | boolean | Whether the property is defined |
|---|---|---|
Detaches an existing event handler from this component.
This method is the opposite of on().
Note: in case wildcard pattern is passed for event name, only the handlers registered with this wildcard will be removed, while handlers registered with plain names matching this wildcard will remain.
See also on().
| public boolean off ( $name, $handler = null ) | ||
| $name | string | Event name |
| $handler | callable | The event handler to be removed. If it is null, all handlers attached to the named event will be removed. |
| return | boolean | If a handler is found and detached |
|---|---|---|
Attaches an event handler to an event.
The event handler must be a valid PHP callback. The following are some examples:
function ($event) { ... } // anonymous function
[$object, 'handleClick'] // $object->handleClick()
['Page', 'handleClick'] // Page::handleClick()
'handleClick' // global function handleClick()
The event handler must be defined with the following signature,
function ($event)
where $event is an yii\base\Event object which includes parameters associated with the event.
Since 2.0.14 you can specify event name as a wildcard pattern:
$component->on('event.group.*', function ($event) {
Yii::trace($event->name . ' is triggered.');
});
See also off().
| public void on ( $name, $handler, $data = null, $append = true ) | ||
| $name | string | The event name |
| $handler | callable | The event handler |
| $data | mixed | The data to be passed to the event handler when the event is triggered. When the event handler is invoked, this data can be accessed via yii\base\Event::$data. |
| $append | boolean | Whether to append new event handler to the end of the existing handler list. If false, the new handler will be inserted at the beginning of the existing handler list. |
Triggers an event.
This method represents the happening of an event. It invokes all attached handlers for the event including class-level handlers.
| public void trigger ( $name, yii\base\Event $event = null ) | ||
| $name | string | The event name |
| $event | yii\base\Event | The event parameter. If not set, a default yii\base\Event object will be created. |