A service locator is an object that knows how to provide all sorts of services (or components) that an application
might need. Within a service locator, each component has only a single instance which is uniquely identified by an ID.
might need. Within a service locator, each component exists as only a single instance, uniquely identified by an ID.
You use the ID to retrieve a component from the service locator.
In Yii, a service locator is simply an instance of [[yii\di\ServiceLocator]] or its child class.
In Yii, a service locator is simply an instance of [[yii\di\ServiceLocator]], or from a child class.
The most commonly used service locator in Yii is the *application* object which can be accessed through
`\Yii::$app`. The services it provides are called *application components*, such as the `request`, `response`,
`urlManager` components. You may configure these components or even replace them with your own implementations easily
The most commonly used service locator in Yii is the *application* object, which can be accessed through
`\Yii::$app`. The services it provides are called *application components*, such as the `request`, `response`, and
`urlManager` components. You may configure these components, or even replace them with your own implementations, easily
through functionality provided by the service locator.
Besides the application object, each module object is also a service locator.
To use a service locator, the first step is to register components. A component can be registered
To use a service locator, the first step is to register components with it. A component can be registered
via [[yii\di\ServiceLocator::set()]]. The following code shows different ways of registering components:
```php
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@@ -43,7 +43,7 @@ $locator->set('search', function () {
$locator->set('pageCache',newFileCache);
```
Once a component is registered, you can access it using its ID in one of the following two ways:
Once a component has been registered, you can access it using its ID, in one of the two following ways:
```php
$cache=$locator->get('cache');
...
...
@@ -53,7 +53,7 @@ $cache = $locator->cache;
As shown above, [[yii\di\ServiceLocator]] allows you to access a component like a property using the component ID.
When you access a component for the first time, [[yii\di\ServiceLocator]] will use the component registration
information to create a new instance of the component and return it. Later if the component is accessed again,
information to create a new instance of the component and return it. Later, if the component is accessed again,
the service locator will return the same instance.
You may use [[yii\di\ServiceLocator::has()]] to check if a component ID has already been registered.
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@@ -61,9 +61,8 @@ If you call [[yii\di\ServiceLocator::get()]] with an invalid ID, an exception wi
Because service locators are often being created with [configurations](concept-configurations.md),
a writable property named [[yii\di\ServiceLocator::setComponents()|components]] is provided so that
you can configure it and register multiple components at once. The following code shows a configuration array
that can be used to configure an application and register the "db", "cache" and "search" components:
a writable property named [[yii\di\ServiceLocator::setComponents()|components]] is provided. This allows you to configure and register multiple components at once. The following code shows a configuration array
that can be used to configure an application, while also registering the "db", "cache" and "search" components:
