桥接模式（C++实现）——我们来一起画个有颜色的图

桥接模式（bridge pattern）

感觉桥接模式是一种挺灵活的设计模式吧，它可以很好的把各个类串在一起。比如说你走进了一家4S店，准备去买辆跑车。跑车的颜色可以是一个类，跑车的形状可以是一个类，跑车的品牌也是一个类。你告诉店家你想要一辆流线型的黑色兰博基尼，店家就会按照你的需求带你去看车了，你作为客户是看不到流线型的黑色兰博基尼的实现过程，而店家就是你的那个桥，对外直接暴露接口，满足你要流线型的黑色兰博基尼的需求。
另外如果你还想多了解的话，这里推荐一篇博文，感觉也解释的挺好的——设计模式读书笔记-----桥接模式

UML图

这里举一个画图的例子

桥接模式主要解决的是如何把各个细节的类串联起来，满足调用者的需求。有点像小时候玩的十字路口游戏，每走到一个分叉路口，都需要做出你的选择，不断地选择之后最后有了只属于你的结果，人生大概也是如此吧-_-

代码实现

bridge.h

#ifndef _BRIDGE_
#define _BRIDGE_

#include <iostream>
#include <string>

using namespace std;

class shape
{
public:
    virtual void draw() = 0;
};

class circle:public shape
{
public:
    void draw()
    {
        cout << "draw circle." << endl;
    }
};

class square:public shape
{
public:
    void draw()
    {
        cout << "draw square." << endl;
    }
};

class color
{
public:
    virtual void fill() = 0;
};

class red:public color
{
public:
    void fill()
    {
        cout << "fill red." << endl;
    }
}; 

class green:public color
{
public:
    void fill()
    {
        cout << "fill green." << endl;
    }
};

class bridge
{
private:
    shape *m_shape;
    color *m_color;

public:
    bridge()
    {
        m_shape = NULL;
        m_color = NULL;
    }
    ~bridge()
    {
        if (m_color != NULL)
            delete m_color;
        if (m_shape != NULL)
            delete m_shape;
    }
    void draw_shape_with_color(string shape_type, string color_type)
    {
        if (m_color != NULL)
        {
            delete m_color;
            m_color = NULL;
        }
        if (m_shape != NULL)
        {
            delete m_shape;
            m_shape = NULL;
        }
        if (shape_type == "circle")
            m_shape = new circle;
        else if (shape_type == "square")
            m_shape = new square;
        else
        {
            cout << "There is no this shape:" << shape_type << endl;
            return;
        }
        if (color_type == "red")
            m_color = new red;
        else if (color_type == "green")
            m_color = new green;
        else
        {
            cout << "There is no this color:" << color_type << endl;
            return;
        }
        m_shape->draw();
        m_color->fill();
        cout << endl;
    }
};

#endif

#include "bridge.h"
#include <iostream>
#include <string>

using namespace std;

int main(int argc, char const *argv[])
{
    bridge bridge_demo;
    bridge_demo.draw_shape_with_color("circle", "red");
    bridge_demo.draw_shape_with_color("circle", "black");
    return 0;
}

结果