# Class yii\behaviors\AttributeBehavior

Inheritance | yii\behaviors\AttributeBehavior » yii\base\Behavior » yii\base\BaseObject
Implements | yii\base\Configurable
Subclasses | yii\behaviors\BlameableBehavior, yii\behaviors\OptimisticLockBehavior, yii\behaviors\SluggableBehavior, yii\behaviors\TimestampBehavior
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/behaviors/AttributeBehavior.php

AttributeBehavior automatically assigns a specified value to one or multiple attributes of an ActiveRecord object when certain events happen.

To use AttributeBehavior, configure the $attributes property which should specify the list of attributes that need to be updated and the corresponding events that should trigger the update. Then configure the $value property with a PHP callable whose return value will be used to assign to the current attribute(s). For example,

    use yii\behaviors\AttributeBehavior;

    public function behaviors()
    {
        return [
            [
                'class' => AttributeBehavior::className(),
                'attributes' => [
                    ActiveRecord::EVENT_BEFORE_INSERT => 'attribute1',
                    ActiveRecord::EVENT_BEFORE_UPDATE => 'attribute2',
                ],
                'value' => function ($event) {
                    return 'some value';
                },
            ],
        ];
    }

Because attribute values will be set automatically by this behavior, they are usually not user input and should therefore not be validated, i.e. they should not appear in the rules() method of the model.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$attributes | array | List of attributes that are to be automatically filled with the value specified via $value. | yii\behaviors\AttributeBehavior
$owner | yii\base\Component|null | The owner of this behavior | yii\base\Behavior
$preserveNonEmptyValues | boolean | Whether to preserve non-empty attribute values. | yii\behaviors\AttributeBehavior
$skipUpdateOnClean | boolean | Whether to skip this behavior when the `$owner` has not been modified | yii\behaviors\AttributeBehavior
$value | mixed | The value that will be assigned to the current attributes. | yii\behaviors\AttributeBehavior

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\BaseObject
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of an object property. | yii\base\BaseObject
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\BaseObject
__set() | Sets value of an object property. | yii\base\BaseObject
__unset() | Sets an object property to null. | yii\base\BaseObject
attach() | Attaches the behavior object to the component. | yii\base\Behavior
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\BaseObject
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\BaseObject
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
detach() | Detaches the behavior object from the component. | yii\base\Behavior
evaluateAttributes() | Evaluates the attribute value and assigns it to the current attributes. | yii\behaviors\AttributeBehavior
events() | Declares event handlers for the $owner's events. | yii\behaviors\AttributeBehavior
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\BaseObject
hasProperty() | Returns a value indicating whether a property is defined. | yii\base\BaseObject
init() | Initializes the object. | yii\base\BaseObject

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
getValue() | Returns the value for the current attributes. | yii\behaviors\AttributeBehavior

## Property Details

$attributes public property

List of attributes that are to be automatically filled with the value specified via $value. The array keys are the ActiveRecord events upon which the attributes are to be updated, and the array values are the corresponding attribute(s) to be updated. You can use a string to represent a single attribute, or an array to represent a list of attributes. For example,

    [
        ActiveRecord::EVENT_BEFORE_INSERT => ['attribute1', 'attribute2'],
        ActiveRecord::EVENT_BEFORE_UPDATE => 'attribute2',
    ]

public array $attributes = []
$preserveNonEmptyValues public property (available since version 2.0.13)

Whether to preserve non-empty attribute values.

public boolean $preserveNonEmptyValues = false
$skipUpdateOnClean public property (available since version 2.0.8)

Whether to skip this behavior when the `$owner` has not been modified

public boolean $skipUpdateOnClean = true
$value public property

The value that will be assigned to the current attributes. This can be an anonymous function, callable in array format (e.g. `[$this, 'methodName']`), an Expression object representing a DB expression (e.g. `new Expression('NOW()')`), scalar, string or an arbitrary value. If the former, the return value of the function will be assigned to the attributes. The signature of the function should be as follows,

    function ($event)
    {
        // return value will be assigned to the attribute
    }

public mixed $value = null

## Method Details

evaluateAttributes() public method

Evaluates the attribute value and assigns it to the current attributes.

public void evaluateAttributes ( $event )
$event | yii\base\Event |

events() public method

Declares event handlers for the $owner's events.

Child classes may override this method to declare what PHP callbacks should be attached to the events of the $owner component.

The callbacks will be attached to the $owner's events when the behavior is attached to the owner; and they will be detached from the events when the behavior is detached from the component.

The callbacks can be any of the following:

- method in this behavior: `'handleClick'`, equivalent to `[$this, 'handleClick']`
- object method: `[$object, 'handleClick']`
- static method: `['Page', 'handleClick']`
- anonymous function: `function ($event) { ... }`

The following is an example:

    [
        Model::EVENT_BEFORE_VALIDATE => 'myBeforeValidate',
        Model::EVENT_AFTER_VALIDATE => 'myAfterValidate',
    ]

public array events ( )
return | array | Events (array keys) and the corresponding event handler methods (array values).

getValue() protected method

Returns the value for the current attributes.

This method is called by evaluateAttributes(). Its return value will be assigned to the attributes corresponding to the triggering event.

protected mixed getValue ( $event )
$event | yii\base\Event | The event that triggers the current attribute updating.
return | mixed | The attribute value