Let's talk in depth about the build() method in laravel container

Laravel is a popular PHP framework that is widely used for web application development. You can quickly build an efficient web application using the Laravel framework. Containers are a very important concept in Laravel. Container is a service container in Laravel, used to manage classes in all applications, especially service providers and dependency injection classes. In Laravel, a very important method of the container is the build() method.

What is a container?

In the Laravel framework, containers are a very important concept, which are used to manage class instances in the application. Laravel registers all classes into the container, making it easy to manage these classes. In the container, Laravel will automatically resolve the dependencies between classes, making it very convenient to use classes.

Constructor method of container

In Laravel, when using a container, we usually use the container constructor method. The purpose of this method is to create a new container instance. When creating a container instance, we can pass the service provider object into the constructor, so that the container will automatically register and resolve the services in the service provider.

use Illuminate\Container\Container;

$container = new Container();

In Laravel, you can use the make() method of the container to obtain the services registered in the container. For example:

$app = $container->make('Illuminate\Contracts\Foundation\Application');

Container’s build method

In Laravel, a very important method in the container is the build() method. build() The function of the method is to create a new class instance. When creating a class instance, the container will automatically parse the constructor of this class and automatically parse all the parameters it requires.

build() The syntax of the method is as follows:

/**
 * Resolve the given type from the container.
 *
 * @param  string  $abstract
 * @param  array   $parameters
 * @return mixed
 */
public function build($abstract, array $parameters = array());

When using the build() method, we need to pass in an abstract class or With the interface name as a parameter, the container will try to create an instance of this class. If the constructor of this class needs to depend on other classes, the container will automatically resolve these dependencies.

For example, we have a service provider class App\Providers\LoggerServiceProvider, which has a method register(). This method will register a log instance to In the container:

use App\Loggers\DatabaseLogger;

class LoggerServiceProvider extends ServiceProvider
{
    public function register()
    {
        $this->app->singleton('logger', function ($app) {
            return new DatabaseLogger($app->make('Illuminate\Database\ConnectionInterface'));
        });
    }
}

In the above code, we use the singleton() method to register a log instance into the container, and specify that this log instance depends on Illuminate\ Database\ConnectionInterface interface. When the container creates a log instance, it will automatically resolve this dependency.

We can use the make() method of the container to obtain this log instance:

$logger = $container->make('logger');

In the above code, the container will automatically parse DatabaseLogger class, and inject the Illuminate\Database\ConnectionInterface interface into this class, and finally return a log instance.

Summary

Containers are a very important concept in Laravel applications. Containers can be used to easily manage class instances in an application, and dependencies between classes can be automatically resolved. When using containers, the build() method is a very important method for creating class instances and automatically resolving dependencies in their constructors.

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