Php Laravel, why give contract to class constructor?

Question

Laravel

I'm studying laravel->contracts and the following question arose:

<?php

namespace App\Orders;

use Illuminate\Contracts\Cache\Repository as Cache;

class Repository
{
    /**
     * Экземпляр кэша.
     */
    protected $cache;

    /**
     * Создание нового экземпляра репозитория.
     *
     * @param  Cache  $cache
     * @return void
     */
    public function __construct(Cache $cache)
    {
        $this->cache = $cache;
    }
}

Why do we need to pass the contract to the constructor, because we need to implement it? Or what I don't understand. Or show an article where it is told.

Answer 1

Google dependency injection laravel.

Answer 2

Try reading the documentation .

Answer 3

The contract implies that it has one main released class. But we can also change it.
For example, with the mysql database, the main one, if it is registered in the config. There are also other database drivers working on a contract basis. Mail, cache, repositories and much more work the same

Answer 4

If you had to implement a contract, then it would be indicated in the class declaration, for example:

class Repository implements RepositoryInterface
или
class Repository extends AbstractRepository

In your example, the Repository class does not implement any contracts. And in the constructor, a ready-made implementation of the contract (that is, an interface) is connected.