设计模式之-简单工厂

在简单工厂模式的最大优点在于工厂类中包含了必要的逻辑判断，根据客户端的选择条件动态实例化相关的类，对于客户端来说，去除了与具体产品的依赖。缺点是违背了“开放-封闭”原则。

示例代码

public class Operation
    {
        private double _numberA = 0;
        private double _numberB = 0;
        public double NumberA
        {
            get;
            set;
        }
        public double NumberB
        {
            get;
            set;
        }
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }
    class OperationAdd:Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA + NumberB;
            return result;
        }
    }
    class OperationSub : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }
    //简单工厂模式，到底实例化谁，将来会不会增加实例化的对象
    public class OperationFactory
    {
        public static Operation createOperate(string operate)
        {
            Operation oper = null;
            switch(operate)
            {
                case "+":
                    oper = new OperationAdd();
                    break;
                case "-":
                    oper = new OperationSub();
                    break;
            }
            return oper;
        }
    }
    static void Main(string[] args)
    {
        Operation oper;
        oper = OperationFactory.createOperate("+");
        oper.NumberA = 1;
        oper.NumberB = 2;
        double result = oper.GetResult();
        Console.WriteLine(result);
    }

UML类图：

 

#include<iostream>
#include<string>
using namespace std;
class Person
{
protected:
    string sex;
public:
    virtual void SetSex()
    {

    }
    virtual string GetSex()
    {
        return sex;
    }
};
class Man :public Person
{
public:
    void SetSex()
    {
        sex = "Man";
    }
    string GetSex()
    {
        return sex;
    }
};
class Woman :public Person
{
public:
    void SetSex()
    {
        sex = "Woman";
    }
    string GetSex()
    {
        return sex;
    }
};
class SampleFactory
{
public:    
    static Person* Produce(char type)
    {
        
        switch (type)
        {
        case'W':
        {
            return(new Woman());
            break;
        }
        case'M':
        {
            return(new Man());
            break;
        }
        }        
    }
};
int main()
{
    Person* p0 = SampleFactory::Produce('W');
    p0->SetSex();
    string result0 = p0->GetSex();
    cout << result0 << endl;

    Person *p1 = SampleFactory::Produce('M');
    p1->SetSex();
    string result1 = p1->GetSex();
    cout << result1 << endl;
    return 0;
}