Question

在Head First Design Pattern一书中，我不明白为什么PizzaTestDrive类会创建SimplePizzaFactory类的对象。为什么PizzaStore类不会创建自己的对象？

public class PizzaTestDrive {

    public static void main(String[] args) {
        SimplePizzaFactory factory = new SimplePizzaFactory();
        PizzaStore store = new PizzaStore(factory);

        Pizza pizza = store.orderPizza("cheese");
        System.out.println("We ordered a " + pizza.getName() + "\n");

        pizza = store.orderPizza("veggie");
        System.out.println("We ordered a " + pizza.getName() + "\n");
    }
}

public class PizzaStore {
    SimplePizzaFactory factory;

    public PizzaStore(SimplePizzaFactory factory) { 
        this.factory = factory;
    }

    public Pizza orderPizza(String type) {
        Pizza pizza;

        pizza = factory.createPizza(type);

        pizza.prepare();
        pizza.bake();
        pizza.cut();
        pizza.box();

        return pizza;
    }

}

abstract public class Pizza {
    String name;
    String dough;
    String sauce;
    ArrayList toppings = new ArrayList();

    public String getName() {
        return name;
    }

    public void prepare() {
        System.out.println("Preparing " + name);
    }

    public void bake() {
        System.out.println("Baking " + name);
    }

    public void cut() {
        System.out.println("Cutting " + name);
    }

    public void box() {
        System.out.println("Boxing " + name);
    }

    public String toString() {
        // code to display pizza name and ingredients
        StringBuffer display = new StringBuffer();
        display.append("---- " + name + " ----\n");
        display.append(dough + "\n");
        display.append(sauce + "\n");
        for (int i = 0; i < toppings.size(); i++) {
            display.append((String )toppings.get(i) + "\n");
        }
        return display.toString();
    }
}

public class SimplePizzaFactory {

    public Pizza createPizza(String type) {
        Pizza pizza = null;

        if (type.equals("cheese")) {
            pizza = new CheesePizza();
        } else if (type.equals("pepperoni")) {
            pizza = new PepperoniPizza();
        } else if (type.equals("clam")) {
            pizza = new ClamPizza();
        } else if (type.equals("veggie")) {
            pizza = new VeggiePizza();
        }
        return pizza;
    }
}

public class CheesePizza extends Pizza {
    public CheesePizza() {
        name = "Cheese Pizza";
        dough = "Regular Crust";
        sauce = "Marinara Pizza Sauce";
        toppings.add("Fresh Mozzarella");
        toppings.add("Parmesan");
    }
}

public class ClamPizza extends Pizza {
    public ClamPizza() {
        name = "Clam Pizza";
        dough = "Thin crust";
        sauce = "White garlic sauce";
        toppings.add("Clams");
        toppings.add("Grated parmesan cheese");
    }
}


public class PepperoniPizza extends Pizza {
    public PepperoniPizza() {
        name = "Pepperoni Pizza";
        dough = "Crust";
        sauce = "Marinara sauce";
        toppings.add("Sliced Pepperoni");
        toppings.add("Sliced Onion");
        toppings.add("Grated parmesan cheese");
    }
}


public class VeggiePizza extends Pizza {
    public VeggiePizza() {
        name = "Veggie Pizza";
        dough = "Crust";
        sauce = "Marinara sauce";
        toppings.add("Shredded mozzarella");
        toppings.add("Grated parmesan");
        toppings.add("Diced onion");
        toppings.add("Sliced mushrooms");
        toppings.add("Sliced red pepper");
        toppings.add("Sliced black olives");
    }
}

比萨饼准备披萨。 SimplePizzaFactory选择将要制作的披萨。 PizzaStore将披萨“卖”给客户。而PizzaTestDrive就是客户。

Answer 1

因为作者选择以这种方式设计它。

您可能会将其视为比萨店从工厂获取冷冻比萨饼，然后准备，烘焙，切割和装箱。

该设计将创建比萨饼的责任与名称（这就是PizzaFactory所做的）以及将其煮熟和盒装出售给顾客（这就是PizzaStore的作用）分开了。

PizzaStore可以选择使用另一家披萨供应商，这会以不同的方式制作比萨饼。但是比萨饼店的准备，烘焙和装箱仍然会以同样的方式运作。

工厂模式首先

1 个答案: