策略模式(Strategy)

最新推荐文章于 2025-02-18 07:32:03 发布

xufei96

最新推荐文章于 2025-02-18 07:32:03 发布

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分类专栏：设计模式笔记

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本文介绍了策略模式的实现方式，并展示了如何将策略模式与简单工厂模式相结合。通过C#和Python两种语言的示例代码，详细说明了策略模式及上下文类的使用方法。

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UML类图：

代码示例：

    //策略类
    public abstract class Animal
    {
        public abstract void Run();
    }

    public class Dog : Animal
    {
        public override void Run()
        {
            Console.WriteLine("Dog was running...");
        }
    }

    public class Cat : Animal
    {
        public override void Run()
        {
            Console.WriteLine("Cat was running...");
        }
    }
    //Context类，维护一个Animal实例
    public class AnimalContext
    {
        public Animal AnimalInstance { get; set; }

        public AnimalContext(Animal animal)
        {
            this.AnimalInstance = animal;
        }
    }

策略与简单工厂结合：

    //策略类
    public abstract class Animal
    {
        public abstract void Run();
    }

    public class Dog : Animal
    {
        public override void Run()
        {
            Console.WriteLine("Dog was running...");
        }
    }

    public class Cat : Animal
    {
        public override void Run()
        {
            Console.WriteLine("Cat was running...");
        }
    }
    //Context类，维护一个Animal实例
    public class AnimalContext
    {
        public Animal AnimalInstance { get; set; }

        public AnimalContext(string animalType)   //工厂类与Context类合并，构造函数参数string类型
        {
            switch(animalType)
            {
                case "Dog":
                    this.AnimalInstance = new Dog();
                    break;
                case "Cat":
                    this.AnimalInstance = new Cat();
                    break;
                default:
                    this.AnimalInstance = null;
                    break;
            }
        }
    }

Python版本

>>> class BaseClass:
... 	def BaseFunc(self):
... 		raise NotImplimentedError("abstract")
... 	
>>> class ClassA(BaseClass):
... 	def BaseFunc(self):
... 		return "This is ClassA"
... 	
>>> class ClassB(BaseClass):
... 	def BaseFunc(self):
... 		return "This is ClassB"
... 	
>>> class ClassContext:
... 	BaseClassInstance=None
... 	def Func(self):
... 		return self.BaseClassInstance.BaseFunc()
... 
>>> classContext=ClassContext()
>>> classContext.BaseClassInstance=ClassA()
>>> classContext.Func()
'This is ClassA'
>>> classContext.BaseClassInstance=ClassB()
>>> classContext.Func()
'This is ClassB'
>>>

与简单工厂的结合使用:

>>> class ClassContext:
... 	__baseClassInstance=None
... 	def GetInstance(self, classStr):
... 		if(classStr=="ClassA"):
... 			self.__baseClassInstance=ClassA()
... 		elif(classStr=="ClassB"):
... 			self.__baseClassInstance=ClassB()
... 		else:
... 			pass
... 	def Func(self):
... 		return self.__baseClassInstance.BaseFunc()
... 
>>> classContext=ClassContext()
>>> classContext.GetInstance("ClassA")
>>> classContext.Func()
'This is ClassA'
>>> classContext.GetInstance("ClassB")
>>> classContext.Func()
'This is ClassB'
>>>