《大话设计模式》读书笔记之C++实现--chapter15抽象工厂模式

#include <iostream>using namespace std;//抽象产品类class AbstractProduct{public:    virtual void ProductFunction() = 0;     //子类可以重写该函数来实现不同子类的特有功能    virtual ~AbstractProduct(){}};//具体产品类，有实现自己功能的成员函数class ConcreteProductA:public AbstractProduct{public:    void ProductFunction()    {        cout << "ConcreteProductA do its function" << endl;    }};class ConcreteProductB:public AbstractProduct{public:    void ProductFunction()    {        cout << "ConcreteProductB do its function" << endl;    }};//抽象工厂类，可以生产不同的产品class AbstractFactory{public:    virtual AbstractProduct* CreateProduct() = 0;    virtual ~AbstractFactory(){}};class ConcreteFactoryA:public AbstractFactory{public:    AbstractProduct* CreateProduct()    {        return new ConcreteProductA();    }};class ConcreteFactoryB:public AbstractFactory{public:    AbstractProduct* CreateProduct()    {        return new ConcreteProductB();    }};int main(int argc,char** argv){    AbstractFactory *factoryA = new ConcreteFactoryA();    AbstractFactory *factoryB = new ConcreteFactoryB();    AbstractProduct *productA = factoryA->CreateProduct();    AbstractProduct *productB = factoryB->CreateProduct();    productA->ProductFunction();    productB->ProductFunction();    return 0;}

以下是书中具体的一个DB例子

#include <iostream>using namespace std;class User{};class IUser{public:    virtual void Insert(User user) = 0;    virtual void GetId(User user) = 0;};class SqlServerUser:public IUser{public:    void Insert(User user)    {        cout << "use sqlserver insert into user" << endl;    }    void GetId(User user)    {        cout << "use sqlserver get user id " << endl;    }};class AccessUser:public IUser{public:    void Insert(User user)    {        cout << "use AccessUser insert into user" << endl;    }    void GetId(User user)    {        cout << "use AccessUser get user id " << endl;    }};class IFactory{public:    virtual IUser* CreateUser() = 0;};class SqlServerFactory:public IFactory{public:    IUser* CreateUser()    {        return new SqlServerUser();    }};class AcceseFactory:public IFactory{public:    IUser* CreateUser()    {        return new AccessUser();    }};int main(int argc,char** argv){    User user;    IFactory* access = new AcceseFactory();    IUser* accessUser = access->CreateUser();    accessUser->Insert(user);    return 0;}

利用简单工厂来改进抽象工厂，也就是将选择工厂转移到类中决定，而不必通过继承的各种子类来决定

#include <iostream>#include <string>using namespace std;//抽象产品类class AbstractProduct{public:    virtual void ProductFunction() = 0;     //子类可以重写该函数来实现不同子类的特有功能    virtual ~AbstractProduct(){}};//具体产品类，有实现自己功能的成员函数class ConcreteProductA:public AbstractProduct{public:    void ProductFunction()    {        cout << "ConcreteProductA do its function" << endl;    }};class ConcreteProductB:public AbstractProduct{public:    void ProductFunction()    {        cout << "ConcreteProductB do its function" << endl;    }};//产品枚举类，代表不同产品enum ProductType{    ConcreteA,    ConcreteB};//抽象工厂类，可以生产不同的产品class Factory{public:    static AbstractProduct* CreateProduct()    {        switch (m_ProductType) {        case ConcreteA:            return new ConcreteProductA();            break;        case ConcreteB:            return new ConcreteProductB();            break;        default:            return nullptr;            break;        }    }private:    static ProductType m_ProductType;};//在类外初始化static数据成员并决定生成哪种产品ProductType Factory::m_ProductType = ConcreteB;int main(int argc,char** argv){    AbstractProduct *product = Factory::CreateProduct();    product->ProductFunction();    return 0;}