# Abstract Class yii\caching\Dependency

Inheritance | yii\caching\Dependency » yii\base\BaseObject
Implements | yii\base\Configurable
Subclasses | yii\caching\ChainedDependency, yii\caching\DbDependency, yii\caching\DbQueryDependency, yii\caching\ExpressionDependency, yii\caching\FileDependency, yii\caching\TagDependency
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/caching/Dependency.php

Dependency is the base class for cache dependency classes.

Child classes should override its generateDependencyData() for generating the actual dependency data.

For more details and usage information on Cache, see the guide article on caching.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$data | mixed | The dependency data that is saved in cache and later is compared with the latest dependency data. | yii\caching\Dependency
$reusable | boolean | Whether this dependency is reusable or not. | yii\caching\Dependency

## Public Methods

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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
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
evaluateDependency() | Evaluates the dependency by generating and saving the data related with dependency. | yii\caching\Dependency
getHasChanged() | Returns a value indicating whether the dependency has changed. | yii\caching\Dependency
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
isChanged() | Checks whether the dependency is changed. | yii\caching\Dependency
resetReusableData() | Resets all cached data for reusable dependencies. | yii\caching\Dependency

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
generateDependencyData() | Generates the data needed to determine if dependency is changed. | yii\caching\Dependency
generateReusableHash() | Generates a unique hash that can be used for retrieving reusable dependency data. | yii\caching\Dependency

## Property Details

$data public property

The dependency data that is saved in cache and later is compared with the latest dependency data.

public mixed $data = null
$reusable public property

Whether this dependency is reusable or not. True value means that dependent data for this cache dependency will be generated only once per request. This allows you to use the same cache dependency for multiple separate cache calls while generating the same page without an overhead of re-evaluating dependency data each time. Defaults to false.

public boolean $reusable = false

## Method Details

evaluateDependency() public method

Evaluates the dependency by generating and saving the data related with dependency.

This method is invoked by cache before writing data into it.

public void evaluateDependency ( $cache )
$cache | yii\caching\CacheInterface | The cache component that is currently evaluating this dependency

generateDependencyData() protected abstract method

Generates the data needed to determine if dependency is changed.

Derived classes should override this method to generate the actual dependency data.

protected abstract mixed generateDependencyData ( $cache )
$cache | yii\caching\CacheInterface | The cache component that is currently evaluating this dependency
return | mixed | The data needed to determine if dependency has been changed.

generateReusableHash() protected method

Generates a unique hash that can be used for retrieving reusable dependency data.

See also $reusable.

protected string generateReusableHash ( )
return | string | A unique hash value for this cache dependency.

getHasChanged() public method
Deprecated since version 2.0.11. Will be removed in version 2.1. Use isChanged() instead.

Returns a value indicating whether the dependency has changed.

public boolean getHasChanged ( $cache )
$cache | yii\caching\CacheInterface | The cache component that is currently evaluating this dependency
return | boolean | Whether the dependency has changed.

isChanged() public method (available since version 2.0.11)

Checks whether the dependency is changed.

public boolean isChanged ( $cache )
$cache | yii\caching\CacheInterface | The cache component that is currently evaluating this dependency
return | boolean | Whether the dependency has changed.

resetReusableData() public static method

Resets all cached data for reusable dependencies.

public static void resetReusableData ( )