Clean Code

範例：咖啡機（介面隔離原則）

Principle: 介面隔離原則

情境：目前我們有一台全自動咖啡機

  • 首先定義全自動咖啡機介面
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<?php

namespace App\SOLID\ISP\CoffeeMachine\Contracts;

interface AutomaticCoffeeMachineInterface
{
    public function grind($coffeeBeans);

    public function brew($coffeePowder);
}

  • 接著是全自動咖啡機
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<?php

namespace App\SOLID\ISP\CoffeeMachine;

use App\SOLID\ISP\CoffeeMachine\Contracts\AutomaticCoffeeMachineInterface;

class AutomaticCoffeeMachine implements AutomaticCoffeeMachineInterface
{
    public function grind($coffeeBeans)
    {
        if ($coffeeBeans == '咖啡豆') {
            return '咖啡粉';
        }
    }

    public function brew($coffeePowder)
    {
        if ($coffeePowder == '咖啡粉') {
            return '咖啡';
        }
    }
}
  • 最後是目前的沖煮方式
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<?php

namespace App\SOLID\ISP\CoffeeMachine;

class Program
{
    protected $coffeeGrinder;

    protected $coffeeMaker;

    public function getCoffeeByAutomaticCoffeeMachine($coffeeBeans)
    {
        $automaticCoffeeMachine = new AutomaticCoffeeMachine();
        $this->coffeeGrinder = $automaticCoffeeMachine;
        $this->coffeeMaker = $automaticCoffeeMachine;

        return $this->getCoffee($coffeeBeans);
    }

    private function grind($coffeeBeans)
    {
        return $this->coffeeGrinder->grind($coffeeBeans);
    }

    private function brew($coffeePowder)
    {
        return $this->coffeeMaker->brew($coffeePowder);
    }

    private function getCoffee($coffeeBeans)
    {
        $coffeePowder = $this->grind($coffeeBeans);
        $coffee = $this->brew($coffeePowder);
        return $coffee;
    }
}

然而，隨著對咖啡興趣增加，我們想來玩玩摩卡壺。
卻發現摩卡壺不會磨粉…

需求一：將全自動咖啡機介面職責分離，拆分出磨粉介面與沖煮介面

  • 首先定義磨粉介面
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<?php

namespace App\SOLID\ISP\CoffeeMachine\Contracts;

interface CoffeeGrinder
{
    public function grind($coffeeBeans);
}

  • 接著定義沖煮介面
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<?php

namespace App\SOLID\ISP\CoffeeMachine\Contracts;

interface CoffeeMaker
{
    public function brew($coffeePowder);
}

  • 最後修改原本的全自動咖啡機，讓它實作新的兩個介面
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<?php

namespace App\SOLID\ISP\CoffeeMachine;

use App\SOLID\ISP\CoffeeMachine\Contracts\CoffeeGrinder;
use App\SOLID\ISP\CoffeeMachine\Contracts\CoffeeMaker;

class AutomaticCoffeeMachine implements CoffeeGrinder, CoffeeMaker
{
    public function grind($coffeeBeans)
    {
        if ($coffeeBeans == '咖啡豆') {
            return '咖啡粉';
        }
    }

    public function brew($coffeePowder)
    {
        if ($coffeePowder == '咖啡粉') {
            return '咖啡';
        }
    }
}

需求二：實作磨豆機與摩卡壺

  • 實作磨豆機（因為拆分出沖煮介面，它不需要知道如何沖煮）
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<?php

namespace App\SOLID\ISP\CoffeeMachine;

use App\SOLID\ISP\CoffeeMachine\Contracts\CoffeeGrinder;

class NormalCoffeeGrinder implements CoffeeGrinder
{
    public function grind($coffeeBeans)
    {
        if ($coffeeBeans == '咖啡豆') {
            return '咖啡粉';
        }
    }
}

  • 實作摩卡壺（因為拆分出磨豆介面，它不需要知道如何磨豆）
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<?php

namespace App\SOLID\ISP\CoffeeMachine;

use App\SOLID\ISP\CoffeeMachine\Contracts\CoffeeMaker;

class Mocalpot implements CoffeeMaker
{
    public function brew($coffeePowder)
    {
        if ($coffeePowder == '咖啡粉') {
            return '咖啡';
        }
    }
}

  • 最後新增煮咖啡的方法，用磨豆機與摩卡壺的組合
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<?php

namespace App\SOLID\ISP\CoffeeMachine;

use App\SOLID\ISP\CoffeeMachine\Contracts\CoffeeGrinder;
use App\SOLID\ISP\CoffeeMachine\Contracts\CoffeeMaker;
use App\SOLID\ISP\CoffeeMachine\NormalCoffeeGrinder;
use App\SOLID\ISP\CoffeeMachine\MocalPot;

class Program
{
    /**
     * @var CoffeeGrinder
     */
    protected $coffeeGrinder;

    /**
     * @var CoffeeMaker
     */
    protected $coffeeMaker;

    public function getCoffeeByAutomaticCoffeeMachine($coffeeBeans)
    {
        $automaticCoffeeMachine = new AutomaticCoffeeMachine();
        $this->setCoffeeGrinder($automaticCoffeeMachine);
        $this->setCoffeeMaker($automaticCoffeeMachine);

        return $this->getCoffee($coffeeBeans);
    }

    public function getCoffeeByNormalCoffeeGrinderAndMocalPot($coffeeBeans)
    {
        $normalCoffeeGrinder = new NormalCoffeeGrinder();
        $mocalPot = new MocalPot();
        $this->setCoffeeGrinder($normalCoffeeGrinder);
        $this->setCoffeeMaker($mocalPot);

        return $this->getCoffee($coffeeBeans);
    }

    private function grind($coffeeBeans)
    {
        return $this->coffeeGrinder->grind($coffeeBeans);
    }

    private function brew($coffeePowder)
    {
        return $this->coffeeMaker->brew($coffeePowder);
    }

    private function getCoffee($coffeeBeans)
    {
        $coffeePowder = $this->grind($coffeeBeans);
        $coffee = $this->brew($coffeePowder);
        return $coffee;
    }

    private function setCoffeeGrinder(CoffeeGrinder $coffeeGrinder)
    {
        $this->coffeeGrinder = $coffeeGrinder;
    }

    private function setCoffeeMaker(CoffeeMaker $coffeeMaker)
    {
        $this->coffeeMaker = $coffeeMaker;
    }
}

ʕ •ᴥ•ʔ：運用介面隔離原則拆分介面職責，
我們就可以玩更多花樣的咖啡沖煮方法了。

而煮咖啡方法也不必因為器具更換而修改。
符合開放封閉原則。