esase / tiny-service-manager

The Service Manager is a service/object locator, tasked with retrieving other objects.

tiny-service-manager

Tiny/Service Manager - it's a very simple realization of DI (dependency injection) container with a clean and understandable Api. (There are no any extra dependencies and it's very small).

DI containers are essential part of any modern framework or CMS. Differently speaking it's the one of the most important part in web applications, which stores and produces any kind of services for you (controllers, services, utilities, etc).

Furthermore it follows to a one of the SOLID. principle (dependency injection or dependency inversion). Which stands for - you should not create objects directly in other objects, because of some difficulties in unit testing and maintaining of embedded classes. Lets check a look a couple of examples:

a wrong way:

<?php

class A {
    private B $embedded;

    public function __construct() {
        // Issues:
        // 1. we cannot test it because we cannot mimic it
        // 2. If we decide to use another implementation we will have to find and replace all its references
        $this->embedded = new B();
    }
}

the best way - is to inject any dependencies in constructor or setters (if dependencies are optional).

<?php

class A {
    private B $embedded;

    public function __construct(B $embedded) {
        $this->embedded = $embedded;
    }
}

service manager in action

    use Tiny\ServiceManager\ServiceManager;

    // The Service Manager is a service/object locator, tasked with retrieving other objects.
    $serviceManager = new ServiceManager([
        B::class => function(ServiceManager $serviceManager) {
            return new B();
        },
        A::class => function(ServiceManager $serviceManager) {
            return new A($serviceManager->get(B::class));
        }
    ]);

    // now whenever we get an instance of "A" class we get it with injected instance of "B" class
    $serviceA = $serviceManager->get(A::class);

now we can easily test the A class injecting a mocked version of the B

$serviceA = new A(new MockedB());

For more details please check a look the documentation link below.

Installation

Run the following to install this library:

$ composer require esase/tiny-service-manager

Documentation

https://tiny-docs.readthedocs.io/en/latest/tiny-service-manager/docs/index.html