2022-08-01 工厂方法模式

工厂方法 == 开闭原则 + 简单工厂

一.优点

1. 实现了对象创建和使⽤的分离。
2. 系统的可扩展性也就变得⾮常好，⽆需修改接⼝和原类。

二.缺点

1. 增加了类的个数，增加了系统的抽象性和理解难度

三.使用场景

1. 调用者不知道它所需要的对象的类。
2. 抽象⼯⼚类通过其⼦类工厂来指定创建哪个对象。

//Fruit.h
#pragma once
#include <string>
//抽象水果类
class Fruit
{
public:
    virtual std::string GetName() = 0;
};
//苹果类:public Fruit
class Apple :public Fruit
{
public:
    std::string GetName() override;
};
//香蕉类:public Fruit
class Banana :public Fruit
{
public:
    std::string GetName() override;
};
//抽象工厂类
class AbstractFactory
{
public:
    virtual Fruit* CreateFruit() = 0;
};
//苹果工厂类:public AbstractFactory
class AppleFactory :public AbstractFactory
{
public:
    Fruit* CreateFruit() override;
};
class BananaFactory :public AbstractFactory
{
public:
    Fruit* CreateFruit() override;
};
//Fruit.cpp
#include "Fruit.h"
#include <iostream>
std::string Apple::GetName()
{
    std::cout << "here is Apple" << std::endl;
    return std::string("Apple");
}
std::string Banana::GetName()
{
    std::cout << "here is Banana" << std::endl;
    return std::string("Banana");
}
Fruit* AppleFactory::CreateFruit()
{
    return new Apple;
}
Fruit* BananaFactory::CreateFruit()
{
    return new Banana;
}
//main.cpp
#include "Fruit.h"
#include <iostream>
int main()
{
    Fruit* apple = nullptr;
    AppleFactory apple_factory;
    apple = apple_factory.CreateFruit();
    std::cout << apple->GetName() << std::endl;
    if (apple!= nullptr)
    {
        delete apple;
        apple = nullptr;
    }
    Fruit* banana = nullptr;
    BananaFactory banana_factory;
    banana = banana_factory.CreateFruit();
    std::cout << banana->GetName() << std::endl;
    if (banana != nullptr)
    {
        delete banana;
        banana = nullptr;
    }
    system("pause");
    return 0;
}