Teach you how to apply the Repository design pattern in Laravel5.8

                                                                                           

The following tutorial column will introduce to you how to correctly apply the Repository design pattern in Laravel 5.8. I hope it will be helpful to friends in need!

In this article, I will show you how to implement the

repository design pattern from scratch in Laravel. I will be using Laravel version 5.8.3, but Laravel version is not the most important. Before you start writing code, you need to know some information about

repository

design patterns.

repository Design patterns allow you to work with objects without knowing how those objects are persisted. Essentially, it is an abstraction of the data layer.

This means that your business logic does not need to know how to retrieve the data or what the data source is, the business logic relies on the repository to retrieve the correct data.

Regarding this pattern, I have seen some misunderstanding it as repository being used to create or update data. This is not what

repository

is supposed to do, repository is not supposed to create or update data, only to retrieve it. Do you understand? Let’s write the code together

Since we’re starting from scratch, let’s create a new Laravel project:

composer create-project --prefer-dist laravel/laravel repository

For this tutorial, we will build a small blogging application. Now that we have created a new Laravel project, we should create a controller and model for it.

php artisan make:controller BlogController

This will create the

BlogController

in the

app/Http/Controllers

directory.

php artisan make:model Models/Blog -m

Tip: The

-m

option will create a corresponding database migration. You can find the generated migration in the *database/migrations directory. *
Now you should be able to find the newly generated model Blog in the

app/Models

directory. This is just a way I like to store my models. Now that we have our controller and model, it’s time to look at the migration file we created. In addition to the default Laravel timestamp fields, our blog only requires the Title, Content, and

UserID

fields.

<?php

use Illuminate\Support\Facades\Schema;use Illuminate\Database\Schema\Blueprint;use Illuminate\Database\Migrations\Migration;class CreateBlogsTable extends Migration{
    public function up()
    {
        Schema::create(&#39;blogs&#39;, function (Blueprint $table) {
            $table->bigIncrements(&#39;id&#39;);
            $table->string(&#39;title&#39;);
            $table->text(&#39;content&#39;);
            $table->integer(&#39;user_id&#39;);
            $table->timestamps();

            $table->foreign(&#39;user_id&#39;)
                  ->references(&#39;id&#39;)
                  ->on(&#39;users&#39;);
        });
    }

    public function down()
    {
        Schema::dropIfExists(&#39;blogs&#39;);
    }}

Tips: If you are using an old version below Laravel 5.8, please replace

$table->bigIncrements('id');

with:

$table->increments('id');

Set up the database

I will use the MySQL database as an example, the first step is to create a new database.

mysql -u root -p 
create database laravel_repository;

The above command will create a new database called laravel_repository. Next we need to add database information to the

.env

file in the Laravel root directory.

DB_DATABASE=laravel_repositoryDB_USERNAME=rootDB_PASSWORD=secret

After you update the .env file we need to clear the cache:

php artisan config:clear

Run the migration

Now we have After setting up the database, you can start running the migration:

php artisan migrate

This will create the

blogs

table, which contains the

title

, we declared in the migration. content and user_id fields. Implementation

repository

Design patternEverything is ready, we can now start to implement the repository design style. We will create the

Repositories

directory inside the app directory. The second directory we will create is the Interfaces directory, which is located within the Repositories directory. In the Interfaces file we will create a

BlogRepositoryInterface

interface that contains two methods. Returns the all

method of all blog posts

1. Returns the getByUser method of all blog posts of a specific user

2. <?php
   
   namespace App\Repositories\Interfaces;use App\User;interface BlogRepositoryInterface{
       public function all();
   
       public function getByUser(User $user);}

   The last class we need to create is BlogRepository
that will implement

BlogRepositoryInterface

, and we will write the simplest implementation.

<?php

namespace App\Repositories;use App\Models\Blog;use App\User;use App\Repositories\Interfaces\BlogRepositoryInterface;class BlogRepository implements BlogRepositoryInterface{
    public function all()
    {
        return Blog::all();
    }

    public function getByUser(User $user)
    {
        return Blog::where(&#39;user_id&#39;,$user->id)->get();
    }}

Your Repositories directory should look like this:

app/└── Repositories/
    ├── BlogRepository.php
    └── Interfaces/
        └── BlogRepositoryInterface.php

You have now successfully created a repository. But we're not done yet, it's time to start using our

repository

.

在控制器中使用 Repository

要开始使用 BlogRepository ，我们首先需要将其注入到 BlogController 。由于 Laravel 的依赖注入，我们很容易用另一个来替换它。这就是我们控制器的样子：

<?php

namespace App\Http\Controllers;use App\Repositories\Interfaces\BlogRepositoryInterface;use App\User;class BlogController extends Controller{
    private $blogRepository;

    public function __construct(BlogRepositoryInterface $blogRepository)
    {
        $this->blogRepository = $blogRepository;
    }

    public function index()
    {
        $blogs = $this->blogRepository->all();

        return view(&#39;blog&#39;)->withBlogs($blogs);
    }

    public function detail($id)
    {
        $user = User::find($id);
        $blogs = $this->blogRepository->getByUser($user);

        return view(&#39;blog&#39;)->withBlogs($blogs);
    }}

如你所见，控制器中的代码很简短，可读性非常的高。不需要十行代码就可以获取到所需的数据，多亏了 repository ，所有这些逻辑都可以在一行代码中完成。这对单元测试也很好，因为 repository 的方法很容易复用。

repository 设计模式也使更改数据源变得更加容易。在这个例子中，我们使用 MySQL 数据库来检索我们的博客内容。我们使用 Eloquent 来完成查询数据库操作。但是假设我们在某个网站上看到了一个很棒的博客 API，我们想使用这个 API 作为数据源，我们所要做的就是重写 BlogRepository 来调用这个 API 替换 Eloquent 。

RepositoryServiceProvider

我们将注入 BlogController 中的 BlogRepository ，而不是注入 BlogController 中的 BlogRepositoryInterface ，然后让服务容器决定将使用哪个存储库。这将在 AppServiceProvider 的 boot 方法中实现，但我更喜欢为此创建一个新的 provider 来保持整洁。

php artisan make:provider RepositoryServiceProvider

我们为此创建一个新的 provider 的原因是，当您的项目开始发展为大型项目时，结构会变得非常凌乱。设想一下，一个拥有 10 个以上模型的项目，每个模型都有自己的 repository ，你的 AppServiceProvider 可读性将会大大降低。

我们的 RepositoryServiceProvider 会像下面这样：

<?php

namespace App\Providers;use App\Repositories\BlogRepository;use App\Repositories\Interfaces\BlogRepositoryInterface;use Illuminate\Support\ServiceProvider;class RepositoryServiceProvider extends ServiceProvider{
    public function register()
    {
        $this->app->bind(
            BlogRepositoryInterface::class, 
            BlogRepository::class
        );
    }}

留意用另一个 repository 替代 BlogRepository 是多么容易！

不要忘记添加 RepositoryServiceProvider 到 config/app.php 文件的 providers 列表中。完成了这些后我们需要清空缓存：

'providers' => [
    //测试￥￥￥￥￥￥￥￥￥￥￥￥￥￥￥￥￥
  \App\Providers\RepositoryServiceProvider::class],

php artisan config:clear

就是这样

现在你已经成功实现了 repository 设计模式，不是很难吧？

你可以选择增加一些路由和视图来拓展代码，但本文将在这里结束，因为本文主要是介绍 repository 设计模式的。

如果你喜欢这篇文章，或者它帮助你实现了 repository 设计模式，请确保你也查看了我的其他文章。如果你有任何反馈、疑问，或希望我撰写另一个有关 Laravel 的主题，请随时发表评论。

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