原型模式（Prototype）

baidu

原型模式是一种创建型设计模式，其功能为复制一个运行时的对象，包括对象各个成员当前的值。而代码又能保持独立性。

场景

举例

假设这样一个场景，孙悟空出世，在花果山经历与猴孙的生死离别后，拜菩提老祖为师。历经多年，学的一身本领。此时的悟空拔出一个毫毛，变出一个自己。

分析

此时悟空变出的另一个自己，自然要与现在的年龄、身高、体重等多个参数一致。如果不加设计，这些代码可能散落在客户端函数。假如过了十年继续施展分身，又需重新假如这些代码。日积月累，这些终将成为晦涩而又难以维护的“一坨”。

实现

对于上述场景就有必要引入原型模式，原型模式的设计也是比较简单的。只需要在类的设计时增加一个clone接口，用于返回当前对象this指针。客户端在使用时，只需要对象的clone接口，就能拿到当前对象的各个成员值。

类图

原型模式

通过原型模式基类规范具备复制接口的子类实现。

源码

#include <iostream>
#include <string>

using namespace std;

class CPrototype
{
public:

    CPrototype() {}

    ~CPrototype() {}

    virtual CPrototype* Clone() = 0;
};

class CWukong : CPrototype
{
public:
    CWukong() : mAge(0), mHeightCM(100), mHair(10000), mLockRing(0), mFightCapacity (20)
    {

     }

    CWukong(CWukong *rhs)
    {
        mName = rhs->mName;
        mAge = rhs->mAge;
        mHeightCM = rhs->mHeightCM;
        mHair = rhs->mHair;
        mLockRing = rhs->mLockRing;
        mFightCapacity = rhs->mFightCapacity;
    }

    virtual ~CWukong() {}

    void SetName(string value) { mName = value; }

    void AddAge(int value) { mAge += value; }

    void SetHeight(int value) { mHeightCM = value; }

    void SetHair(int value) { mHair = value; }

    void PutLockRing() { mLockRing = 1; }

    void RemoveLockRing() { mLockRing = 0; }

    void SetFightCapacity(int value) { mFightCapacity = value; }

    string GetName() { return mName; }

    int GetAge() { return mAge; }

    int GetHeight() { return mHeightCM; }

    int GetHair() { return mHair; }

    int GetLockRing() { return mLockRing; }

    int GetFightCapacity() { return mFightCapacity; }

    CWukong* Clone()
    {
        return new CWukong(*this);
    }

private:
    string mName;
    int mAge;
    int mHeightCM;
    int mHair;
    bool mLockRing;
    int mFightCapacity;
};

static void learn_skills(CWukong *pMonkey)
{
    //After 11 years of study, Wukong's parameters change
    pMonkey->SetName("Wukong.Sun");
    pMonkey->AddAge(11);
    pMonkey->SetHeight(150);
    pMonkey->SetFightCapacity(80);
}

static void show_params(CWukong *pMonkey)
{
    cout << ">> " << pMonkey->GetName() << endl;
    cout << "Age: " << pMonkey->GetAge() << endl;
    cout << "Height(cm): " << pMonkey->GetHeight() << endl;
    cout << "Hair: " << pMonkey->GetHair() << endl;
    cout << "LockRing: " << pMonkey->GetLockRing() << endl;
    cout << "FightCapacity: " << pMonkey->GetFightCapacity() << endl;
    cout << "\n" << endl;
}

int main (int argc, char *argv[])
{
    CWukong *theWukong = new CWukong();
    //Before Learning, show params
    cout << "Before Learning" << endl;
    show_params(theWukong);

    //At the age of five, he went to learn skills
    theWukong->AddAge(5);
    theWukong->SetHeight(120);
    learn_skills(theWukong);
    //Return after Learning, show params
    show_params(theWukong);

    //Show multitasking skills
    cout << "Clone Wukong" << endl;
    CWukong *theWukong2 = theWukong->Clone();
    show_params(theWukong2);

    delete theWukong2;
    delete theWukong;
    return 0;
}

Before Learning
>> 
Age: 0
Height(cm): 100
Hair: 10000
LockRing: 0
FightCapacity: 20


>> Wukong.Sun
Age: 16
Height(cm): 150
Hair: 10000
LockRing: 0
FightCapacity: 80


Clone Wukong
>> Wukong.Sun
Age: 16
Height(cm): 150
Hair: 10000
LockRing: 0
FightCapacity: 80