Day 07: Creational patterns - Abstract Factory

目的

假如产品之间有可以负责联系的元素，那依赖该元素找出共同点後建立关联，进而减少工厂的数量，却可以维持更多的生产。

说明

昨天提到 Factory Method，建立许多工厂来负责生产产品。让我们试想一个情境，现在行销部门决定要建立多种口味的饮料，因此会有樱桃口味、柠檬口味与加盐，套用在现有的三个产品（可乐、矿泉水、柳橙汁），会有九种结果，此时，必须建立多达九个的 Factory 来处理这件事。

可乐 矿泉水 柳橙汁
樱桃口味 樱桃口味可乐 人工樱桃风味矿泉水 樱桃柳橙汁
柠檬口味 柠檬口味可乐 柠檬矿泉水 柠檬柳橙汁
加盐 加盐可乐 加盐矿泉水 加盐柳橙汁

此时，可以使用 Abstract Factory 减少工厂的数量，作法是：

  1. 将原有产品转变成虚拟层，视为亲代，可以用 Abstract Class、Interface。
  2. 原有产品每一个都建立三个口味的子代。
  3. 建立工厂的亲代，可以用 Abstract Class、Interface，负责要求每间口味工厂需要生产三种原有产品。
  4. 建立一系列的口味工厂，每间工厂都可以产出以原有口味为基底的新饮料。
  5. 决策者依据口味使用对应的工厂，好取得对应的新饮料。

UML 图

Abstract Factory Pattern UML Diagram

使用 Java 实作

产品祖代：PETBottle

public abstract class PETBottle {
    protected String smell = "";
    protected String color = "";

    protected PETBottle(String smell, String color) {
        this.smell = smell;
        this.color = color;
    }

    public abstract String getTaste();
}

产品亲代-可乐：Coke

public abstract class Coke extends PETBottle {
    protected Coke(String smell) {
        super(smell, "黑色");
    }

    @Override
    public String getTaste() {
        return "这瓶可乐的颜色：" + color + "，香味是：" + smell;
    }
}

产品子代-可乐相关口味系列：CherryCoke、LemonCoke、SaltCoke

public class CherryCoke extends Coke {
    public CherryCoke() {
        super("樱桃味道");
    }

    @Override
    public String getTaste() {
        return "这瓶樱桃可乐的颜色：" + color + "，香味是：" + smell;
    }
}

public class LemonCoke extends Coke {
    public LemonCoke() {
        super("清新的酸味");
    }

    @Override
    public String getTaste() {
        return "这瓶柠檬可乐的颜色：" + color + "，香味是：" + smell;
    }
}

public class SaltCoke extends Coke {
    public SaltCoke() {
        super("咸咸的");
    }

    @Override
    public String getTaste() {
        return "这瓶加盐可乐的颜色：" + color + "，香味是：" + smell;
    }
}

产品亲代-矿泉水：Water

public abstract class Water extends PETBottle {
    protected Water(String smell) {
        super(smell, "透明");
    }

    @Override
    public String getTaste() {
        return "这瓶水的颜色：" + color + "，香味是：" + smell;
    }
}

产品子代-矿泉水相关口味系列：CherryWater、LemonWater、SaltWater

public class CherryWater extends Water {
    public CherryWater() {
        super("樱桃味道");
    }

    @Override
    public String getTaste() {
        return "这瓶人工樱桃风味矿泉水的颜色：" + color + "，香味是：" + smell;
    }
}

public class LemonWater extends Water {
    public LemonWater() {
        super("清新的酸味");
    }

    @Override
    public String getTaste() {
        return "这瓶柠檬矿泉水的颜色：" + color + "，香味是：" + smell;
    }
}

public class SaltWater extends Water {
    public SaltWater() {
        super("咸咸的");
    }

    @Override
    public String getTaste() {
        return "这瓶加盐矿泉水的颜色：" + color + "，香味是：" + smell;
    }
}

产品亲代-柳橙汁：OrangeJuice

public abstract class OrangeJuice extends PETBottle {
    protected OrangeJuice(String smell) {
        super(smell, "橘色");
    }

    @Override
    public String getTaste() {
        return "这瓶柳橙汁的颜色：" + color + "，香味是：" + smell;
    }
}

产品子代-柳橙汁相关口味系列：CherryOrangeJuice、LemonOrangeJuice、SaltOrangeJuice

public class CherryOrangeJuice extends OrangeJuice {
    public CherryOrangeJuice() {
        super("樱桃味道");
    }

    @Override
    public String getTaste() {
        return "这瓶樱桃柳橙汁的颜色：" + color + "，香味是：" + smell;
    }
}

public class LemonOrangeJuice extends OrangeJuice {
    public LemonOrangeJuice() {
        super("柑橘类特有的酸味");
    }

    @Override
    public String getTaste() {
        return "这瓶柠檬柳橙汁的颜色：" + color + "，香味是：" + smell;
    }
}

public class SaltOrangeJuice extends OrangeJuice {
    public SaltOrangeJuice() {
        super("咸咸的");
    }

    @Override
    public String getTaste() {
        return "这瓶加盐柳橙汁的颜色：" + color + "，香味是：" + smell;
    }
}

工厂亲代：BeverageFactory

public interface BeverageFactory {
    Coke produceCoke();

    Water produceWater();

    OrangeJuice produceOrangeJuice();
}

工厂子代-相关口味系列：CherryFlavorFactory、LemonFlavorFactory、SaltFlavorFactory

public class CherryFlavorFactory implements BeverageFactory {
    @Override
    public Coke produceCoke() {
        return new CherryCoke();
    }

    @Override
    public Water produceWater() {
        return new CherryWater();
    }

    @Override
    public OrangeJuice produceOrangeJuice() {
        return new CherryOrangeJuice();
    }
}

public class LemonFlavorFactory implements BeverageFactory {
    @Override
    public Coke produceCoke() {
        return new LemonCoke();
    }

    @Override
    public Water produceWater() {
        return new LemonWater();
    }

    @Override
    public OrangeJuice produceOrangeJuice() {
        return new LemonOrangeJuice();
    }
}

public class SaltFlavorFactory implements BeverageFactory {
    @Override
    public Coke produceCoke() {
        return new SaltCoke();
    }

    @Override
    public Water produceWater() {
        return new SaltWater();
    }

    @Override
    public OrangeJuice produceOrangeJuice() {
        return new SaltOrangeJuice();
    }
}

决策者：

public class BeverageAbstractFactorySample {
    public static void main(String[] args) {
        System.out.println("准备开喝！");
        BeverageFactory saltFlavorFactory = new SaltFlavorFactory();
        Coke saltCoke = saltFlavorFactory.produceCoke();
        Water saltWater = saltFlavorFactory.produceWater();
        OrangeJuice saltOrangeJuice = saltFlavorFactory.produceOrangeJuice();

        System.out.println("盐味派对！");
        System.out.println(saltCoke.getTaste());
        System.out.println(saltWater.getTaste());
        System.out.println(saltOrangeJuice.getTaste());

        System.out.println("\n口味更换");
        BeverageFactory lemonFlavorFactory = new LemonFlavorFactory();
        Coke lemonCoke = lemonFlavorFactory.produceCoke();
        Water lemonWater = lemonFlavorFactory.produceWater();
        OrangeJuice lemonOrangeJuice = lemonFlavorFactory.produceOrangeJuice();

        System.out.println("柠檬派对！");
        System.out.println(lemonCoke.getTaste());
        System.out.println(lemonWater.getTaste());
        System.out.println(lemonOrangeJuice.getTaste());

        System.out.println("\n最後一轮");
        BeverageFactory cherryFlavorFactory = new CherryFlavorFactory();
        Coke cherryCoke = cherryFlavorFactory.produceCoke();
        Water cherryWater = cherryFlavorFactory.produceWater();
        OrangeJuice cherryOrangeJuice = cherryFlavorFactory.produceOrangeJuice();

        System.out.println("樱桃派对！");
        System.out.println(cherryCoke.getTaste());
        System.out.println(cherryWater.getTaste());
        System.out.println(cherryOrangeJuice.getTaste());
    }
}

使用 JavaScript 实作

受限於 JavaScript 没有虚拟型别、无法限制型别。

产品祖代：PETBottle

/** @abstract */
class PETBottle {
  constructor(smell, color) {
    this.smell = smell;
    this.color = color;
  }

  getTaste() { return; }
}

产品亲代-可乐：Coke

/** @abstract */
class Coke extends PETBottle {
  constructor(smell, color) {
    super(smell, "黑色");
  }

  /** @override */
  getTaste() {
    return "这瓶可乐的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

产品子代-可乐相关口味系列：CherryCoke、LemonCoke、SaltCoke

class CherryCoke extends Coke {
  constructor() {
    super("樱桃风味");
  }

  /** @override */
  getTaste() {
    return "这瓶樱桃可乐的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

class LemonCoke extends Coke {
  constructor() {
    super("清新的酸味");
  }

  /** @override */
  getTaste() {
    return "这瓶柠檬可乐的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

class SaltCoke extends Coke {
  constructor() {
    super("咸咸的");
  }

  /** @override */
  getTaste() {
    return "这瓶加盐可乐的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

产品亲代-矿泉水：Water

/** @abstract */
class Water extends PETBottle {
  constructor(smell) {
    super(smell, "透明");
  }

  /** @override */
  getTaste() {
    return "这瓶水的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

产品子代-矿泉水相关口味系列：CherryWater、LemonWater、SaltWater

class CherryWater extends Water {
  constructor() {
    super("樱桃味道");
  }

  /** @override */
  getTaste() {
    return "这瓶人工樱桃风味矿泉水的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

class LemonWater extends Water {
  constructor() {
    super("清新的酸味");
  }

  /** @override */
  getTaste() {
    return "这瓶柠檬矿泉水的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

class SaltWater extends Water {
  constructor() {
    super("咸咸的");
  }

  /** @override */
  getTaste() {
    return "这瓶加盐矿泉水的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

产品亲代-柳橙汁：OrangeJuice

/** @abstract */
class OrangeJuice extends PETBottle {
  constructor(smell) {
    super(smell, "橘色");
  }

  /** @override */
  getTaste() {
    return "这瓶柳橙汁的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

产品子代-柳橙汁相关口味系列：CherryOrangeJuice、LemonOrangeJuice、SaltOrangeJuice

class CherryOrangeJuice extends OrangeJuice {
  constructor() {
    super("樱桃味道");
  }

  /** @override */
  getTaste() {
    return "这瓶樱桃柳橙汁的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

class LemonOrangeJuice extends OrangeJuice {
  constructor() {
    super("柑橘类特有的酸味");
  }

  /** @override */
  getTaste() {
    return "这瓶柠檬柳橙汁的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

class SaltOrangeJuice extends OrangeJuice {
  constructor() {
    super("咸咸的");
  }

  /** @override */
  getTaste() {
    return "这瓶加盐柳橙汁的颜色：" + this.color + "，香味是：" + this.smell;
  }
}

工厂亲代：BeverageFactory

/** @interface */
class BeverageFactory {
  produceCoke() { return; }

  produceWater() { return; }

  produceOrangeJuice() { return; }
}

工厂子代-相关口味系列：CherryFlavorFactory、LemonFlavorFactory、SaltFlavorFactory

class CherryFlavorFactory extends BeverageFactory {
  /** @override */
  produceCoke() {
    return new CherryCoke();
  }

  /** @override */
  produceWater() {
    return new CherryWater();
  }

  /** @override */
  produceOrangeJuice() {
    return new CherryOrangeJuice();
  }
}

class LemonFlavorFactory extends BeverageFactory {
  /** @override */
  produceCoke() {
    return new LemonCoke();
  }

  /** @override */
  produceWater() {
    return new LemonWater();
  }

  /** @override */
  produceOrangeJuice() {
    return new LemonOrangeJuice();
  }
}

class SaltFlavorFactory extends BeverageFactory {
  /** @override */
  produceCoke() {
    return new SaltCoke();
  }

  /** @override */
  produceWater() {
    return new SaltWater();
  }

  /** @override */
  produceOrangeJuice() {
    return new SaltOrangeJuice();
  }
}

实作：

const beverageAbstractFactorySample = () => {
  console.log("准备开喝！");
  const saltFlavorFactory = new SaltFlavorFactory();
  const saltCoke = saltFlavorFactory.produceCoke();
  const saltWater = saltFlavorFactory.produceWater();
  const saltOrangeJuice = saltFlavorFactory.produceOrangeJuice();

  console.log("盐味派对！");
  console.log(saltCoke.getTaste());
  console.log(saltWater.getTaste());
  console.log(saltOrangeJuice.getTaste());

  console.log("\n口味更换");
  const lemonFlavorFactory = new LemonFlavorFactory();
  const lemonCoke = lemonFlavorFactory.produceCoke();
  const lemonWater = lemonFlavorFactory.produceWater();
  const lemonOrangeJuice = lemonFlavorFactory.produceOrangeJuice();

  console.log("柠檬派对！");
  console.log(lemonCoke.getTaste());
  console.log(lemonWater.getTaste());
  console.log(lemonOrangeJuice.getTaste());

  console.log("\n最後一轮");
  const cherryFlavorFactory = new CherryFlavorFactory();
  const cherryCoke = cherryFlavorFactory.produceCoke();
  const cherryWater = cherryFlavorFactory.produceWater();
  const cherryOrangeJuice = cherryFlavorFactory.produceOrangeJuice();

  console.log("樱桃派对！");
  console.log(cherryCoke.getTaste());
  console.log(cherryWater.getTaste());
  console.log(cherryOrangeJuice.getTaste());
};

beverageAbstractFactorySample();

总结

Abstract Factory 改善了 Factory Method 面对更多种产品时，必须建立各自的工厂导致工厂数量过多的问题。当然，缺点也很明显，「必须找到多种产品之间有没有关联」，如果有才能抽离、转换成关系、建立工厂、减少数量；如果没有则无计可施，只能维持 Factory Method 多工厂的局面。

三个 Factory 模式介绍完毕，接着依照字母顺序，介绍 Builder 模式。


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