//Factory Method（工厂方法-对象创建型）

//别名Virtual Constructor（虚构造器）

//定义一个用于创建目标对象的接口，让子类决定实例化哪一个目标类。

//Factory Method 使一个类的实例化延迟到其子类。

#include <iostream>

class IProduct

{

public:

virtual ~IProduct() {}

};

class AProduct : public IProduct {};

class BProduct : public IProduct {};

//方式1：Creator/Factory缺省实现+参数化工厂方法

//（简单工厂）

class SimpleFactory

{

public:

virtual IProduct* create(int type) {

switch (type)

{

case 0: return new AProduct();

case 1: return new BProduct();

default: break;

}

return nullptr;

}

};

//方式2：子类化

class IFactory

{

public:

virtual ~IFactory() {}

virtual IProduct* create() = 0;

};

class AFactory : public IFactory

{

public:

IProduct* create() override {

return new AProduct();

}

};

class BFactory : public IFactory

{

public:

IProduct* create() override {

return new BProduct();

}

};

//测试

void testFactoryMethodPattern()

{

//简单工厂，根据参数来创建对应对象

std::cout << "eg.1" << std::endl;

std::cout << "construct SimpleFactory" << std::endl;

SimpleFactory* f = new SimpleFactory();

std::cout << "SimpleFactory create AProduct through flag" << std::endl;

IProduct* p1 = f->create(0);

std::cout << "AProduct Construction completed" << std::endl;

delete f;

delete p1;

//factory可作为参数传递给类实例，用户再调用factory的create函数

//如我们提供一个带factory参数的接口，后面使用的时候再根据需求创建具体的factory

std::cout << "eg.2" << std::endl;

std::cout << "construct AFactory" << std::endl;

IFactory* factory = new AFactory();

std::cout << "AFactory create AProduct" << std::endl;

IProduct* p2 = factory->create();

std::cout << "AProduct Construction completed" << std::endl;

delete factory;

delete p2;

//

std::cout << "construct BFactory" << std::endl;

factory = new BFactory();

std::cout << "BFactory create BProduct" << std::endl;

p2 = factory->create();

std::cout << "BProduct Construction completed" << std::endl;

delete factory;

delete p2;

}