工厂模式

简单工厂模式

用一个单独的类来做创造实例的过程，就是简单工厂

#include <iostream>
using namespace std;

class AbstractProduct {
public:
    virtual ~AbstractProduct() {} 
    virtual void Operation() = 0;
};

class ProductA : public AbstractProduct {
public:
    void Operation() { cout << "ProductA" << endl; }
};

class ProductB : public AbstractProduct {
public:
    void Operation() { cout << "ProductB" << endl; }
};

class Factory {
public:
    AbstractProduct* createProduct(char product) {
        AbstractProduct* ap = NULL;
        switch(product) {
            case 'A': ap = new ProductA(); break;
            case 'B': ap = new ProductB(); break;
        }
        return ap;
    }
};

int main() {
    Factory* f = new Factory();
    AbstractProduct* apa = f->createProduct('A');
    apa->Operation();  // ProductA

    AbstractProduct* apb = f->createProduct('B');
    apb->Operation();  // ProductB

    delete apa;
    delete apb;
    delete f;

    return 0;
}

缺点：

不符合开闭原则

工厂方法模式

工厂方法模式定义了一个用于创建对象的接口，让子类决定实例化哪一个类

#include <iostream>
using namespace std;

class AbstractProduct
{
public:
    virtual ~AbstractProduct(){}
    virtual void Operation() = 0;
};

class ProductA : public AbstractProduct
{
public:
    void Operation() {cout << "ProductA" << endl;};
};

class ProductB : public AbstractProduct
{
public:
    void Operation() {cout << "ProductB" << endl;};
};

class AbstractFactory
{
public:
    virtual ~AbstractFactory() {}
    virtual AbstractProduct* FactoryMethod() = 0;
};

class FactoryA : public AbstractFactory
{
public:
    ~FactoryA() {}
    ProductA* FactoryMethod(){
        return new ProductA();
    }
};

class FactoryB : public AbstractFactory
{
public:
    ~FactoryB() {}
    ProductB* FactoryMethod(){
        return new ProductB();
    }
};

int main(int argc, const char** argv) {
    AbstractFactory* fa = new FactoryA();
    AbstractProduct* a = fa->FactoryMethod();
    a->Operation();

    AbstractFactory* fb = new FactoryB();
    AbstractProduct* b = fb->FactoryMethod();
    b->Operation();

    delete a;
    delete b;
    delete fa;
    delete fb;

    return 0;
}

抽象工厂模式

抽象工厂模式是工厂方法的进一步深化，在这个模式中，工厂类不单单可以创建一个对象，而是可以创建一组对象。

AbstractFactory（抽象工厂）声明了一组用于创建对象的方法，注意是一组。
ConcreteFactory（具体工厂）：它实现了在抽象工厂中声明的创建对象的方法，生成一组具体对象。
AbstractProduct（抽象产品）：它为每种对象声明接口，在其中声明了对象所具有的业务方法。
ConcreteProduct（具体产品）：它定义具体工厂生产的具体对象。

#include <iostream>
using namespace std;

class AbstractProductA {
public:
    virtual ~AbstractProductA(){}
    virtual void Operation() = 0;
};

class ProductA1 : public AbstractProductA {
public:
    void Operation() {
        cout << "ProductA1" << endl;
    }
};

class ProductA2 : public AbstractProductA {
public:
    void Operation() {
        cout << "ProductA2" << endl;
    }
};

class AbstractProductB {
public:
    virtual ~AbstractProductB(){}
    virtual void Operation() = 0;
};

class ProductB1 : public AbstractProductB {
public:
    void Operation() {
        cout << "ProductB1" << endl;
    }
};

class ProductB2 : public AbstractProductB {
public:
    void Operation() {
        cout << "ProductB2" << endl;
    }
};


class AbstractFactory {
public:
    virtual AbstractProductA* CreateProductA() = 0;
    virtual AbstractProductB* CreateProductB() = 0;
    virtual ~AbstractFactory(){}
};

class ConcreteFactory1 : public AbstractFactory {
public:
    ProductA1* CreateProductA() {
        return new ProductA1();
    }
    ProductB1* CreateProductB() {
        return new ProductB1();
    }
};

class ConcreteFactory2 : public AbstractFactory {
public:
    ProductA2* CreateProductA() {
        return new ProductA2();
    }
    ProductB2* CreateProductB() {
        return new ProductB2();
    }
};

int main() {
    AbstractFactory* af1 = new ConcreteFactory1();
    // 具体工厂创建对应的具体产品
    AbstractProductA* apa1 = af1->CreateProductA();  // 工厂1创建产品A
    apa1->Operation();  // ProductA1

    AbstractProductB* apb1 = af1->CreateProductB();  // 工厂1创建产品B
    apb1->Operation();  // ProductB1

    AbstractFactory* af2 = new ConcreteFactory2();
    AbstractProductA* apa2 = af2->CreateProductA();  // 工厂2创建产品A
    apa2->Operation();  // ProductA2

    AbstractProductB* apb2 = af2->CreateProductB();  // 工厂2创建产品B
    apb2->Operation();  // ProductB2

    delete apa1;
    delete apa2;
    delete af1;
    delete apb1;
    delete apb2;
    delete af2;
    return 0;
}