享元模式（c++實現）

阿新 • • 發佈：2020-07-17

享元模式

享元模式

模式定義

享元模式（Flyweight），運用共享技術有效的支援大量細粒度的物件。

模式動機

如果一個應用使用了大量的物件，而大量的這些物件造成了很大的儲存開銷時就應該考慮使用。
當物件的大多數狀態可以外部狀態，如果刪除物件的外部狀態，那麼可以用相對較少的共享記憶體物件取代很多組物件，此時可以考慮使用享元模式。

UML類圖

原始碼實現

piece.h

#include <string>

enum Color

{

    white,

    black

};

class Piece

{

public:
 

    Piece(Color color);

    void setPoint(int x, int y);

    Color GetColor() const;

public:

    int     m_X;

    int     m_Y;

private:

    Color     m_Color;

};

piece.cpp

#include "piece.h"

Piece::Piece(Color color)

    :m_Color(color)

{

}

void Piece::setPoint(int x, int y)

{

    m_X = x;
 

    m_Y = y;

}

Color Piece::GetColor() const

{

    return m_Color;

}

checkerboard.h

#include <string>

#include "piece.h"

class CheckerBoard

{

public:

    CheckerBoard();

    void Draw();

    void refresh();

    void GetPiece(const Piece& piece);

private:

    std::string     m_Checker;
 

};

checkerboard.cpp

#include <iostream>

#include <string.h>

#include "checkerboard.h"

CheckerBoard::CheckerBoard()

{

    for(int m = 0; m < 20; ++m)

    {

        for(int n = 0; n < 20; ++n)

            m_Checker.append("o");

        m_Checker.append("\n");

    }

}

void CheckerBoard::Draw()

{

    std::cout << m_Checker;

}

void CheckerBoard::refresh()

{

    system("cls");

    std::cout << m_Checker;

}

void CheckerBoard::GetPiece(const Piece& piece)

{

    int pos;

    pos = (piece.m_Y * 21) + piece.m_X;

    if(piece.GetColor() == Color::white)

        m_Checker.replace(pos, 1, "-");

    else if(piece.GetColor() == Color::black)

        m_Checker.replace(pos, 1, "+");

}

piecefactory.h

#include <map>

#include "piece.h"

class PieceFactory

{

public:

    PieceFactory();

    Piece *find(Color color);

private:

    std::map<Color, Piece*>     m_PiecesMap;

};

piecefactory.cpp

#include <memory>

#include "piecefactory.h"

PieceFactory::PieceFactory()

{

}

Piece *PieceFactory::find(Color color)

{

    auto piece = m_PiecesMap.find(color);

    if(piece != m_PiecesMap.end()){

        return piece->second;

    }

    else

    {

        Piece* p = new Piece(color);

        m_PiecesMap[color] = p;

        return p;

    }

}

main.cpp

/************************************

    * @brief	: 享元模式

    * @author	:   wzx

    * @date	:   2020-07-16

    * @project	:  FlyWeight

*************************************/

#include <iostream>

#include <random>

#include <time.h>

#include <thread>

#include <unistd.h>

#include "checkerboard.h"

#include "piecefactory.h"

#include "piece.h"

using namespace std;

void GeneratePoint(Piece* p)

{//隨機數生成有點問題

    std::mt19937 rnd(time(0));

    p->m_X = rnd()%20;

    p->m_Y = rnd()%20;

}

int main()

{

    CheckerBoard board;

    board.Draw();

    PieceFactory factory;

    for(int n = 0; n < 20; ++n)

    {

        Piece* p1 = factory.find(Color::black);

        GeneratePoint(p1);

        sleep(1);

        Piece* p2 = factory.find(Color::white);

        GeneratePoint(p2);

        board.GetPiece(*p2);

        board.GetPiece(*p1);

        board.refresh();

    }

    return 0;

}

執行結果

oooooooooooooooooooo

oooooooooo+ooooooooo

-+oooooooooooooooooo

oooooooooooooooooooo

ooooooo-oooo+oo+oooo

oooooooooooooooooooo

o+oooooooooooooooooo

oooo++oo+ooooooooooo

注：隨機數生成演演算法有點問題，這裡忽略最終結果