Unity实现设计模式——模板方法模式

模板模式(Template Pattern)， 指在一个抽象类公开定义了执行它的方法的模板。它的子类可以按需要重写方法实现，但调用将以抽象类中定义的方式进行。
简单说， 模板方法模式定义一个操作中的算法的骨架，而将这些步骤延迟到子类中，使得子类可以不改变一个算法的结构，就可以重定义该算法的某些特定步骤。

注意模板方法模式和策略模式的区别
模板模式注意强调了抽象类公开定义了一个执行的模板方法，而策略模式是对单个算法的封装更具有独立性

下面使用两个例子去介绍模板方法模式：

1.第一个例子（使用比较抽象的例子）

（一）AbstractClass

abstract class AbstractClass
{
    public abstract void PrimitiveOperation1();
    public abstract void PrimitiveOperation2();

    // The "Template method"
    public void TemplateMethod()
    {
        PrimitiveOperation1();
        PrimitiveOperation2();
        Debug.Log("");
    }
}

（二）ConcreteClassA

class ConcreteClassA : AbstractClass
{
    public override void PrimitiveOperation1()
    {
        Debug.Log("ConcreteClassA.PrimitiveOperation1()");
    }
    public override void PrimitiveOperation2()
    {
        Debug.Log("ConcreteClassA.PrimitiveOperation2()");
    }
}

（三）ConcreteClassB

class ConcreteClassB : AbstractClass
{
    public override void PrimitiveOperation1()
    {
        Debug.Log("ConcreteClassB.PrimitiveOperation1()");
    }
    public override void PrimitiveOperation2()
    {
        Debug.Log("ConcreteClassB.PrimitiveOperation2()");
    }
}

（四）测试

public class TemplateMethodStructure : MonoBehaviour
{
	void Start ( )
	{
        AbstractClass aA = new ConcreteClassA();
        aA.TemplateMethod();

        AbstractClass aB = new ConcreteClassB();
        aB.TemplateMethod();

    }
}

2.第二个例子（使用一个三明治的制作过程来介绍）

（一）Hoagie 三明治抽象基类

    public abstract class Hoagie
    {
        public void MakeSandwich()
        {
            Debug.Log("Making new Sandwich");

            CutBun();

            if (CustomerWantsMeat())
            {
                AddMeat();
            }

            if (CustomerWantsCheese())
            {
                AddCheese();
            }

            if (CustomerWantsVegetables())
            {
                AddVegetables();
            }

            if (CustomerWantsCondiments())
            {
                AddCondiments();
            }

            WrapTheHoagie();
        }
        protected abstract void AddMeat();
        protected abstract void AddCheese();
        protected abstract void AddVegetables();
        protected abstract void AddCondiments();

        protected virtual bool CustomerWantsMeat() { return true; } // << called Hook
        protected virtual bool CustomerWantsCheese() { return true; }
        protected virtual bool CustomerWantsVegetables() { return true; }
        protected virtual bool CustomerWantsCondiments() { return true; }

        protected void CutBun()
        {
            Debug.Log("Bun is Cut");
        }

        protected void WrapTheHoagie()
        {
            Debug.Log("Hoagie is wrapped.");
        }
    }

（二）ItalienHoagie 法式三明治

    public class ItalienHoagie : Hoagie
    {
        protected override void AddMeat()
        {
            Debug.Log("Adding the Meat: Salami");
        }

        protected override void AddCheese()
        {
            Debug.Log("Adding the Cheese: Provolone");
        }

        protected override void AddVegetables()
        {
            Debug.Log("Adding the Vegetables: Tomatoes");
        }

        protected override void AddCondiments()
        {
            Debug.Log("Adding the Condiments: Vinegar");
        }
    }

（三）VeggieHoagie 素菜三明治

    public class VeggieHoagie : Hoagie
    {
        protected override void AddMeat()
        {
        }

        protected override void AddCheese()
        {
        }

        protected override void AddVegetables()
        {
            Debug.Log("Adding the Vegetables: Tomatoes");
        }

        protected override void AddCondiments()
        {
            Debug.Log("Adding the Condiments: Vinegar");
        }

        protected override bool CustomerWantsMeat() { return false; }
        protected override bool CustomerWantsCheese() { return false; }

    }

（四）错误的方式

namespace BadExample
    {
        // this way you would have to rewrite a lot of code
        // especially if something changes or another class differs and does e.g. not AddMeat()
        public class ItalienHoagie
        {
            public void MakeSandwich()
            {
                CutBun();
                AddMeat();
                AddCheese();
                AddVegtables();
                AddCondiments();
                WrapHoagie();
            }

            public void CutBun()
            {
                Debug.Log("Hoagie is Cut");
            }

            public void AddMeat()
            {
                Debug.Log("Added Meat");
            }

            public void AddCheese()
            {
                Debug.Log("Added Cheese");
            }

            public void AddVegtables()
            {
                Debug.Log("Added Vegies");
            }

            public void AddCondiments()
            {
                Debug.Log("Added Condiments");
            }

            public void WrapHoagie()
            {
                Debug.Log("Wrapped Hoagie");
            }
        }
    }

（五）测试

    public class TemplateMethodPatternExample1 : MonoBehaviour
    {
        void Start()
        {
            Hoagie cust12Hoagie = new ItalienHoagie();
            cust12Hoagie.MakeSandwich();

            Hoagie cust13Hoagie = new VeggieHoagie();
            cust13Hoagie.MakeSandwich();
        }
    }