ProtoType(原型）-对象创建型模式

1.意图

用原型实例指定创建对象的种类，并且通过拷贝这些原型创建新的对象。

2.动机

通过拷贝或者“克隆”一个类的实例来创建新的实例。

3.适用性

当一个系统应该独立于它的产品创建、构成和表示时，要使用Prototype模式；以及

• 当要实例化的类是在运行时刻指定时，例如，通过动态装载；或者
• 为了避免创建一个与产品类层次平行的工厂类层次时或者
• 当一个类的实例只能有几个不同状态组合中的一种时。建立相应数目的原型并克隆它们，可能比每次用合适的状态手工实例化该类更方便一些。

4.结构

5.代码实例

#include <memory>

class Prototype
{
public:
    virtual std::shared_ptr<Prototype> Clone() = ;
    virtual void PrintState() = ;
    virtual void SetState(int state) = ;
};

class ConcretePrototype1 : public Prototype
{
public:
    ConcretePrototype1(int state);
    std::shared_ptr<Prototype> Clone();
    void PrintState();
    virtual void SetState(int state);
private:
    int m_iState;
};

class ConcretePrototype2 : public Prototype
{
public:
    ConcretePrototype2(int state);
    std::shared_ptr<Prototype> Clone();
    void PrintState();
    virtual void SetState(int state);
private:
    int m_iState;
};

Prototype.h

#include<map>
#include<memory>

class Prototype;

class ProtoTypeFactory
{
public:
    void RegisterPrototype(int key,std::shared_ptr<Prototype> pProtoType);
    std::shared_ptr<Prototype> GetProtoType(int key);
    void PrintAllPrototypeState();
private:
    std::map<int,std::shared_ptr<Prototype>> m_ProtoTypeMap;
};

ProtoTypeFactory.h

#include "Prototype.h"
#include <iostream>

ConcretePrototype1::ConcretePrototype1(int state) : m_iState(state)
{
}

std::shared_ptr<Prototype> ConcretePrototype1::Clone()
{
    std::shared_ptr<Prototype> pProtoType(new ConcretePrototype1(*this));

    return pProtoType;
}

void ConcretePrototype1::PrintState()
{
    std::cout << " ConcretePrototype1 State is :" << m_iState <<std::endl;
}

void ConcretePrototype1::SetState(int state)
{
    m_iState = state;
}

ConcretePrototype2::ConcretePrototype2(int state) : m_iState(state)
{
}

std::shared_ptr<Prototype> ConcretePrototype2::Clone()
{
    std::shared_ptr<Prototype> pProtoType(new ConcretePrototype2(*this));

    return pProtoType;
}

void ConcretePrototype2::PrintState()
{
    std::cout << " ConcretePrototype2 State is :" << m_iState <<std::endl;
}

void ConcretePrototype2::SetState(int state)
{
    m_iState = state;
}

Prototype.cpp

#include "ProtoTypeFactory.h"
#include "Prototype.h"
#include <utility>

void ProtoTypeFactory::RegisterPrototype(int key,std::shared_ptr<Prototype> pProtoType)
{
    m_ProtoTypeMap[key] = pProtoType;
}

std::shared_ptr<Prototype> ProtoTypeFactory::GetProtoType(int key)
{
    auto iter = m_ProtoTypeMap.find(key);
    return iter->second;
}

void ProtoTypeFactory::PrintAllPrototypeState()
{
    for(auto iter = m_ProtoTypeMap.begin(); iter != m_ProtoTypeMap.end();++iter)
    {
        iter->second->PrintState();
    }
}

ProtoTypeFactory.cpp

#include "ProtoTypeFactory.h"
#include "Prototype.h"
#include <iostream>

void RegisterPrototype(std::shared_ptr<ProtoTypeFactory> pProtoTypeFactory)
{
    std::shared_ptr<Prototype> pConcretePrototype1(new ConcretePrototype1());
    std::shared_ptr<Prototype> ConcretePrototype2(new ConcretePrototype2());
    pProtoTypeFactory->RegisterPrototype(,pConcretePrototype1);
    pProtoTypeFactory->RegisterPrototype(,ConcretePrototype2);
}

int main()
{
    std::shared_ptr<ProtoTypeFactory> pProtoTypeFactory(new ProtoTypeFactory());

    std::cout<< "RegisterPrototype in PrototypeFactory";
    std::cout << std::endl;
    std::cout << std::endl;
    std::cout << std::endl;

    RegisterPrototype(pProtoTypeFactory);

    std::cout<< "Print All State in PrototypeFactory:" << std::endl;
    pProtoTypeFactory->PrintAllPrototypeState();

    std::cout<< "Clone Prototype 1:" << std::endl;
    auto pProtoType = pProtoTypeFactory->GetProtoType();
    std::cout<< "Print State Before Set State" << std::endl;
    auto pClonedProtoType = pProtoType->Clone();
    pClonedProtoType->PrintState();
    std::cout<< "Print State After Set State" << std::endl;
    pClonedProtoType->SetState();
    pClonedProtoType->PrintState();

    std::cout << std::endl;
    std::cout << std::endl;
    std::cout << std::endl;

    std::cout<< "Clone Prototype 2:" << std::endl;
    pProtoType = pProtoTypeFactory->GetProtoType();
    std::cout<< "Print State Before Set State" << std::endl;
    pClonedProtoType = pProtoType->Clone();
    pClonedProtoType->PrintState();
    std::cout<< "Print State After Set State" << std::endl;
    pClonedProtoType->SetState();
    pClonedProtoType->PrintState();

    std::cout << std::endl;
    std::cout << std::endl;
    std::cout << std::endl;

    std::cout<< "Print All State in PrototypeFactory:" << std::endl;
    pProtoTypeFactory->PrintAllPrototypeState();

    while();

}

Test.cpp

6.测试结果

利用原型设计模式时，可以预先注册所需的原型，然后在使用时根据原型创建实例。

7.效果

• 运行时刻增加和删除产品，Prototype允许只通过注册原型实例就可以将一个新的具体产品类并入系统。
• 改变值以指定新对象
• 改变结构以指定新对象
• 减少子类的构造
• 用类动态配置应用。