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。

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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 Hookprotected 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();}}