抽象工厂模式

frame 1:

#include <iostream>
using namespace std;

class User_less11{
private:
    int _id;
    string _name;
    
public:
    int ID(){ return _id;}
    void setID(int id){_id = id;}
    string Name(){return _name;}
    void setName(string name){_name = name;}
    
};


class IUser_less11{
public:
    virtual ~IUser_less11(){};
    virtual void Insert(User_less11 * user){};
    virtual User_less11 * GetUser(int id){return nullptr;};
};

class SqlserverUser_less11 : public IUser_less11{
public:
    void Insert(User_less11 * user) {
        cout<<"insert a new line into sql"<<endl;
    }
    
    User_less11 * GetUser(int id){
        cout<<"get a user from sql"<<endl;
        return nullptr;
    }
};

class AccessUser_less11:public IUser_less11 {
    
public:
    void Insert(User_less11 * user) {
        cout<<"insert a new line into access"<<endl;
    }
    
    User_less11 * GetUser(int id){
        cout<<"get a user from access"<<endl;
        return nullptr;
    }
};

class Department_less11{
private:
    int _id;
    string _name;
    
public:
    int ID(){ return _id;}
    void setID(int id){_id = id;}
    string Name(){return _name;}
    void setName(string name){_name = name;}
    
};
class IDepartment_le11 {
    
public:
    ~IDepartment_le11(){};
    virtual void Insert(Department_less11 * d){};
    virtual Department_less11 * GetDepartment(int id){return nullptr;};
};

class SqlserverDepartment_less11 : public IDepartment_le11{
public:
    void Insert(Department_less11 * department) {
        cout<<"insert a new department into sql"<<endl;
    }
    
    Department_less11 * GetDepartment(int id){
        cout<<"get a department from sql"<<endl;
        return nullptr;
    }
};

class AccessDepartment_less11:public IDepartment_le11 {
    
public:
    void Insert(Department_less11 * department) {
        cout<<"insert a new department into access"<<endl;
    }
    
    Department_less11 * GetDepartment(int id){
        cout<<"get a department from access"<<endl;
        return nullptr;
    }
};



class IFactory_less11 {
    
public:
    ~IFactory_less11(){};
    virtual IUser_less11 * CreateUser(){return nullptr;};
    virtual IDepartment_le11 * CreateDepartment(){return nullptr;};

};

class SqlServerFactory_less11:public IFactory_less11
{
public:
    
    IUser_less11 * CreateUser(){
        return new SqlserverUser_less11();
    }
    
    IDepartment_le11 * CreateDepartment(){return new SqlserverDepartment_less11();}
};

class AccessFactory_less11:IFactory_less11 {
public:
    IUser_less11 * CreateUser(){
        return new AccessUser_less11();
    }
    IDepartment_le11 * CreateDepartment(){return new AccessDepartment_less11();}
    
};

用工厂模式的时候，我们就要在修改需求的时候改变很多的工厂声明的地方，不是很方便。

#include <iostream>
using namespace std;

class User_less11{
private:
    int _id;
    string _name;
    
public:
    int ID(){ return _id;}
    void setID(int id){_id = id;}
    string Name(){return _name;}
    void setName(string name){_name = name;}
    
};


class IUser_less11{
public:
    virtual ~IUser_less11(){};
    virtual void Insert(User_less11 * user){};
    virtual User_less11 * GetUser(int id){return nullptr;};
};

class SqlserverUser_less11 : public IUser_less11{
public:
    void Insert(User_less11 * user) {
        cout<<"insert a new line into sql"<<endl;
    }
    
    User_less11 * GetUser(int id){
        cout<<"get a user from sql"<<endl;
        return nullptr;
    }
};

class AccessUser_less11:public IUser_less11 {
    
public:
    void Insert(User_less11 * user) {
        cout<<"insert a new line into access"<<endl;
    }
    
    User_less11 * GetUser(int id){
        cout<<"get a user from access"<<endl;
        return nullptr;
    }
};

class Department_less11{
private:
    int _id;
    string _name;
    
public:
    int ID(){ return _id;}
    void setID(int id){_id = id;}
    string Name(){return _name;}
    void setName(string name){_name = name;}
    
};
class IDepartment_le11 {
    
public:
    ~IDepartment_le11(){};
    virtual void Insert(Department_less11 * d){};
    virtual Department_less11 * GetDepartment(int id){return nullptr;};
};

class SqlserverDepartment_less11 : public IDepartment_le11{
public:
    void Insert(Department_less11 * department) {
        cout<<"insert a new department into sql"<<endl;
    }
    
    Department_less11 * GetDepartment(int id){
        cout<<"get a department from sql"<<endl;
        return nullptr;
    }
};

class AccessDepartment_less11:public IDepartment_le11 {
    
public:
    void Insert(Department_less11 * department) {
        cout<<"insert a new department into access"<<endl;
    }
    
    Department_less11 * GetDepartment(int id){
        cout<<"get a department from access"<<endl;
        return nullptr;
    }
};

class DataAccess {
protected:
    static const string db;
    
public:
    
    static IUser_less11 * CreateUser(){
        IUser_less11 * result = nullptr;
        if (db == "sqlserver") {
            result = new SqlserverUser_less11();
        } else if (db == "access") {
            result = new AccessUser_less11();
        } else {
            
        }
        return result;
    }

    static IDepartment_le11 * CreateDepartment(){
        IDepartment_le11 * result = nullptr;
        if (db == "sqlserver") {
            result = new SqlserverDepartment_less11();
        } else if (db == "access") {
            result = new AccessDepartment_less11();
        }
        return result;
    }
};

const string DataAccess::db = "sqlserver";

fame3

#include <iostream>
using namespace std;

class User_less11{
private:
    int _id;
    string _name;
    
public:
    int ID(){ return _id;}
    void setID(int id){_id = id;}
    string Name(){return _name;}
    void setName(string name){_name = name;}
    
};


class IUser_less11{
public:
    virtual ~IUser_less11(){};
    virtual void Insert(User_less11 * user){};
    virtual User_less11 * GetUser(int id){return nullptr;};
};

class SqlserverUser_less11 : public IUser_less11{
public:
    void Insert(User_less11 * user) {
        cout<<"insert a new line into sql"<<endl;
    }
    
    User_less11 * GetUser(int id){
        cout<<"get a user from sql"<<endl;
        return nullptr;
    }
};

class AccessUser_less11:public IUser_less11 {
    
public:
    void Insert(User_less11 * user) {
        cout<<"insert a new line into access"<<endl;
    }
    
    User_less11 * GetUser(int id){
        cout<<"get a user from access"<<endl;
        return nullptr;
    }
};

class Department_less11{
private:
    int _id;
    string _name;
    
public:
    int ID(){ return _id;}
    void setID(int id){_id = id;}
    string Name(){return _name;}
    void setName(string name){_name = name;}
    
};
class IDepartment_le11 {
    
public:
    ~IDepartment_le11(){};
    virtual void Insert(Department_less11 * d){};
    virtual Department_less11 * GetDepartment(int id){return nullptr;};
};

class SqlserverDepartment_less11 : public IDepartment_le11{
public:
    void Insert(Department_less11 * department) {
        cout<<"insert a new department into sql"<<endl;
    }
    
    Department_less11 * GetDepartment(int id){
        cout<<"get a department from sql"<<endl;
        return nullptr;
    }
};

class AccessDepartment_less11:public IDepartment_le11 {
    
public:
    void Insert(Department_less11 * department) {
        cout<<"insert a new department into access"<<endl;
    }
    
    Department_less11 * GetDepartment(int id){
        cout<<"get a department from access"<<endl;
        return nullptr;
    }
};

class DataAccess {
protected:
    static const string db;
    
public:
    
    static IUser_less11 * CreateUser(){
        IUser_less11 * result = nullptr;
        if (db == "sqlserver") {
            result = new SqlserverUser_less11();
        } else if (db == "access") {
            result = new AccessUser_less11();
        } else {
            
        }
        return result;
    }

    static IDepartment_le11 * CreateDepartment(){
        IDepartment_le11 * result = nullptr;
        if (db == "sqlserver") {
            result = new SqlserverDepartment_less11();
        } else if (db == "access") {
            result = new AccessDepartment_less11();
        }
        return result;
    }
};

const string DataAccess::db = "sqlserver";

抽象工厂的好处是易于交换产品，由于具体工厂类在一个应用中只需要初始化的时候出现一次，这使得改变一个应用的具体工厂变的十分容易，它只需要改变具体工厂即可使用不同的产品配置。
第二大好处是，它让具体创建实例过程与客户端分离，客户端是通过它们的抽象接口操作实例，产品的具体类名也被具体的工厂实现分离，不会出现在客户代码中。