managing class dependencies and performing dependency injection.

Dependency injection is a fancy phrase that essentially means this: class dependencies are "injected" into the class via the constructor or, in some cases, "setter" methods.

Almost all of your service container bindings will be registered within service providers, so most of these examples will demonstrate using the container in that context.

There is no need to bind classes into the container if they do not depend on any interfaces. The container does not need to be instructed on how to build these objects, since it can automatically resolve these objects using reflection.

Simple Bindings

Within a service provider, you always have access to the container via the $this->app property. We can register a binding using the bind method, passing the class or interface name that we wish to register along with a Closure that returns an instance of the class:

$this->app->bind('HelpSpot\API', function ($app) { return new HelpSpot\API($app->make('HttpClient')); });

Note that we receive the container itself as an argument to the resolver. We can then use the container to resolve sub-dependencies of the object we are building.

Binding A Singleton 单例

The singleton method binds a class or interface into the container that should only be resolved one time. Once a singleton binding is resolved, the same object instance will be returned on subsequent calls into the container:

$this->app->singleton('HelpSpot\API', function ($app) { return new HelpSpot\API($app->make('HttpClient')); });

Binding Instances

You may also bind an existing object instance into the container using the instance method. The given instance will always be returned on subsequent calls into the container:

$api = new HelpSpot\API(new HttpClient); $this->app->instance('HelpSpot\Api', $api);

Binding Primitives绑定常用的基本类型

Sometimes you may have a class that receives some injected classes, but also needs an injected primitive value such as an integer. You may easily use contextual binding to inject any value your class may need:

$this->app->when('App\Http\Controllers\UserController') ->needs('$variableName') ->give($value);

Binding Interfaces To Implementations

$this->app->bind( 'App\Contracts\EventPusher', 'App\Services\RedisEventPusher' );

Contextual Binding

解析：

You may use the make method to resolve a class instance out of the container. The make method accepts the name of the class or interface you wish to resolve:

$api = $this->app->make('HelpSpot\API');

The service container fires an event each time it resolves an object. You may listen to this event using the resolving method:

allowing you to set any additional properties on the object before it is given to its consumer.