認識 Laravel Service Container 服務容器

Laravel
, ,

前言

Laravel 服務容器是管理類別依賴與執行依賴注入的工具。依賴注入指的是：類別的依賴透過建構子「注入」，或在某些情況下透過「setter」方法注入。

由於被注入的類別可以更容易地抽換成其他的實作，所以我們可以很容易地「mock」，或者建立一個假的類別實作來測試我們的應用程式。

簡易綁定

首先新增一個路由在 routes/web.php 檔。

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Route::get('pay', 'OrderController@store');

新增一個 OrderController 控制器。

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php artisan make:controller OrderController

新增一個 app/Billing/PaymentGateway.php 檔，做為一個付款的閘道器。

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namespace App\Billing;

use Illuminate\Support\Str;

class PaymentGateway
{
    public function charge(int $amount)
    {
        return [
            'amount' => $amount,
            'confirmation_number' => Str::random(),
        ];
    }
}

修改 OrderController 控制器：

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namespace App\Http\Controllers;

use App\Billing\PaymentGateway;

class OrderController extends Controller
{
    public function store()
    {
        $paymentGateway = new PaymentGateway();

        dd($paymentGateway->charge(2500));
    }
}

結果：

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array:2 [▼
  "amount" => 2500
  "confirmation_number" => "XvS8O4BNLrhz6gUK"
]

修改 OrderController 控制器，將 PaymentGateway 閘道器改為依賴注入的方式：

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namespace App\Http\Controllers;

use App\Billing\PaymentGateway;

class OrderController extends Controller
{
    public function store(PaymentGateway $paymentGateway)
    {
        dd($paymentGateway->charge(2500));
    }
}

一樣可以運作：

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array:2 [▼
  "amount" => 2500
  "confirmation_number" => "iB3HK755ZMqo7ob0"
]

但是如果有參數要放進 PaymentGateway 閘道器的建構子，像是：

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namespace App\Billing;

use Illuminate\Support\Str;

class PaymentGateway
{
    private $currency;

    public function __construct(string $currency)
    {
        $this->currency = $currency;
    }

    public function charge(int $amount)
    {
        return [
            'amount' => $amount,
            'confirmation_number' => Str::random(),
            'currency' => $this->currency,
        ];
    }
}

就會出錯，因為我們沒有提供參數給它：

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Illuminate\Contracts\Container\BindingResolutionException
Unresolvable dependency resolving [Parameter #0 [ <required> string $currency ]] in class App\Billing\PaymentGateway

因此我們需要在 app/Providers/AppServiceProvider.php 服務提供者中註冊一個容器綁定。

首先透過 $this->app 物件屬性來取得整個應用程式容器，並使用 bind() 方法註冊一個綁定，傳遞一組希望綁定的類別或介面名稱作為第一個參數，接著第二個參數放入用來回傳類別實例的閉包。

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namespace App\Providers;

use App\Billing\PaymentGateway;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->bind(PaymentGateway::class, function ($app) {
            return new PaymentGateway('NTD');
        });
    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }
}

結果：

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array:3 [▼
  "amount" => 2500
  "confirmation_number" => "hZL4jafa5sxY942S"
  "currency" => "NTD"
]

如果有很多個控制器都需要使用這個閘道器，只需要從服務提供者修改參數即可，而不需要到每個控制器去修改。

單例綁定

接下來，在 PaymentGateway 閘道器建立一個 setDiscount() 方法，用來設置折扣金額：

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namespace App\Billing;

use Illuminate\Support\Str;

class PaymentGateway
{
    private $currency;

    private $discount = 0;

    public function __construct(string $currency)
    {
        $this->currency = $currency;
    }

    public function setDiscount(int $amount)
    {
        $this->discount = $amount;
    }

    public function charge(int $amount)
    {
        return [
            'amount' => $amount - $this->discount,
            'confirmation_number' => Str::random(),
            'currency' => $this->currency,
            'discount' => $this->discount,
        ];
    }
}

新增一個 app/Order/OrderDetails.php 檔，用來取得訂單資訊：

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namespace App\Order;

use App\Billing\PaymentGateway;

class OrderDetails
{
    private $paymentGateway;

    public function __construct(PaymentGateway $paymentGateway)
    {
        $this->paymentGateway = $paymentGateway;
    }

    public function all()
    {
        $this->paymentGateway->setDiscount(500);

        return [
            'name' => 'Memo Chou',
            'Address' => 'Taiwan',
        ];
    }
}

修改 OrderController 控制器，使用 all() 方法取得訂單：

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namespace App\Http\Controllers;

use App\Billing\PaymentGateway;
use App\Order\OrderDetails;

class OrderController extends Controller
{
    public function store(OrderDetails $orderDetails, PaymentGateway $paymentGateway)
    {
        $order = $orderDetails->all();

        dd($paymentGateway->charge(2500));
    }
}

結果：

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array:4 [▼
  "amount" => 2500
  "confirmation_number" => "YuVBGKPIqJMrjIij"
  "currency" => "NTD"
  "discount" => 0
]

由於被注入到 OrderDetails 類別和 OrderController 類別的 PaymentGateway 閘道器是兩個不同的實例，所以 discount 會是 0。

我們需要使用 singleton() 方法，將服務提供者所註冊的容器綁定改為單例。被綁定至容器中的類別或介面只會被解析一次，之後的呼叫都會從容器中回傳相同的實例。

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namespace App\Providers;

use App\Billing\PaymentGateway;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->singleton(PaymentGateway::class, function ($app) {
            return new PaymentGateway('NTD');
        });
    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }
}

結果：

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array:4 [▼
  "amount" => 2000
  "confirmation_number" => "F2MFaYLIKFfKl7sD"
  "currency" => "NTD"
  "discount" => 500
]

綁定介面至實作

由於付款方式可能不只一種，因此新增一個 app/Billing/PaymentGatewayContract.php 介面，讓所有的付款方式都去實作：

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namespace App\Billing;

interface PaymentGatewayContract
{
    public function setDiscount(int $amount);

    public function charge(int $amount);
}

將 PaymentGateway 閘道器重新命名為 BankPaymentGateway ，並實作 PaymentGatewayContract 介面。

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namespace App\Billing;

use Illuminate\Support\Str;

class BankPaymentGateway implements PaymentGatewayContract
{
    private $currency;

    private $discount = 0;

    public function __construct(string $currency)
    {
        $this->currency = $currency;
    }

    public function setDiscount(int $amount)
    {
        $this->discount = $amount;
    }

    public function charge(int $amount)
    {
        return [
            'amount' => $amount - $this->discount,
            'confirmation_number' => Str::random(),
            'currency' => $this->currency,
            'discount' => $this->discount,
        ];
    }
}

將 OrderController 控制器中注入的 PaymentGateway 閘道器改為 PaymentGatewayContract 介面：

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namespace App\Http\Controllers;

use App\Billing\PaymentGatewayContract;
use App\Order\OrderDetails;

class OrderController extends Controller
{
    public function store(OrderDetails $orderDetails, PaymentGatewayContract $paymentGateway)
    {
        $order = $orderDetails->all();

        dd($paymentGateway->charge(2500));
    }
}

將 OrderDetails 類別中注入的 PaymentGateway 閘道器也改為 PaymentGatewayContract 介面：

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namespace App\Order;

use App\Billing\PaymentGatewayContract;

class OrderDetails
{
    private $paymentGateway;

    public function __construct(PaymentGatewayContract $paymentGateway)
    {
        $this->paymentGateway = $paymentGateway;
    }

    public function all()
    {
        $this->paymentGateway->setDiscount(500);

        return [
            'name' => 'Memo Chou',
            'Address' => 'Taiwan',
        ];
    }
}

修改 AppServiceProvider 服務提供者，將原先綁定的 PaymentGateway 類別改為 PaymentGatewayContract 介面：

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namespace App\Providers;

use App\Billing\BankPaymentGateway;
use App\Billing\PaymentGatewayContract;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->singleton(PaymentGatewayContract::class, function ($app) {
            return new BankPaymentGateway('NTD');
        });
    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }
}

結果：

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array:4 [▼
  "amount" => 2000
  "confirmation_number" => "quDGIkn79T3dHWD1"
  "currency" => "NTD"
  "discount" => 500
]

接下來，新增一個 CreditPaymentGateway 閘道器，一樣也是實作 PaymentGatewayContract 介面：

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namespace App\Billing;

use Illuminate\Support\Str;

class CreditPaymentGateway implements PaymentGatewayContract
{
    private $currency;

    private $discount = 0;

    public function __construct(string $currency)
    {
        $this->currency = $currency;
    }

    public function setDiscount(int $amount)
    {
        $this->discount = $amount;
    }

    public function charge(int $amount)
    {
        $fees = $amount * 0.03;

        return [
            'amount' => $amount - $this->discount + $fees,
            'confirmation_number' => Str::random(),
            'currency' => $this->currency,
            'discount' => $this->discount,
            'fees' => $fees,
        ];
    }
}

如果要變更付款方式，只要在 AppServiceProvider 服務提供者將要綁定的實例改為 CreditPaymentGateway 閘道器即可。

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namespace App\Providers;

use App\Billing\CreditPaymentGateway;
use App\Billing\PaymentGatewayContract;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->singleton(PaymentGatewayContract::class, function ($app) {
            return new CreditPaymentGateway('NTD');
        });
    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }
}

結果：

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array:5 [▼
  "amount" => 2075.0
  "confirmation_number" => "jOM7mLCGYgIPR1B8"
  "currency" => "NTD"
  "discount" => 500
  "fees" => 75.0
]

如果要動態切換付款方式，只要將服務提供者修改如下即可：

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namespace App\Providers;

use App\Billing\BankPaymentGateway;
use App\Billing\CreditPaymentGateway;
use App\Billing\PaymentGatewayContract;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->singleton(PaymentGatewayContract::class, function ($app) {
            switch (request()->payMethod) {
                case 'bank':
                    return new BankPaymentGateway('NTD');

                default:
                    return new CreditPaymentGateway('NTD');
            }
        });
    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }
}

前往路由 pay?payMethod=bank，結果：

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array:4 [▼
  "amount" => 2000
  "confirmation_number" => "joHVe6Ah19wVZWx5"
  "currency" => "NTD"
  "discount" => 500
]

前往路由 pay?payMethod=credit，結果：

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array:5 [▼
  "amount" => 2075.0
  "confirmation_number" => "s2w2dkTw98XWbkhs"
  "currency" => "NTD"
  "discount" => 500
  "fees" => 75.0
]

建立服務提供者

新增一個獨立的服務提供者來處理付款。

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php artisan make:provider PaymentServiceProvider

將原來寫在 AppServiceProvider 中的容器綁定移至 PaymentServiceProvider 中。

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namespace App\Providers;

use App\Billing\BankPaymentGateway;
use App\Billing\CreditPaymentGateway;
use App\Billing\PaymentGatewayContract;
use Illuminate\Support\ServiceProvider;

class PaymentServiceProvider extends ServiceProvider
{
    /**
     * Register services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->singleton(PaymentGatewayContract::class, function ($app) {
            switch (request()->payMethod) {
                case 'bank':
                    return new BankPaymentGateway('NTD');

                default:
                    return new CreditPaymentGateway('NTD');
            }
        });
    }

    /**
     * Bootstrap services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }
}

在 config/app.php 設定檔中註冊一個服務提供者：

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'providers' => [

    // ...

    /*
    * Application Service Providers...
    */
    App\Providers\AppServiceProvider::class,
    App\Providers\AuthServiceProvider::class,
    // App\Providers\BroadcastServiceProvider::class,
    App\Providers\EventServiceProvider::class,
    App\Providers\RouteServiceProvider::class,
    App\Providers\PaymentServiceProvider::class, // 新增此行

    // ...

],

前往路由 pay?payMethod=bank，結果：

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array:4 [▼
  "amount" => 2000
  "confirmation_number" => "joHVe6Ah19wVZWx5"
  "currency" => "NTD"
  "discount" => 500
]

前往路由 pay?payMethod=credit，結果：

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array:5 [▼
  "amount" => 2075.0
  "confirmation_number" => "s2w2dkTw98XWbkhs"
  "currency" => "NTD"
  "discount" => 500
  "fees" => 75.0
]

參考資料