设计模式：1. 门面模式(Facade)

PROJECT

https://github.com/autoliuweijie/DesignPatterns

Facade Pattern

1. 介绍

1.1 针对问题

1. 系统复杂

   某个系统或者类过于复杂, 使用者需要详细了解内部结构才懂得使用.

1.2 解决方法

1. UML图

   

1.3 优点

1. 降低用户使用系统的难度

   用户不需要对系统内部有足够多的了解, 只需要简单地设置即可.

2. 例子

2.1 需求

1. 需求描述

   照相机需要设置闪光灯, 焦距, 光圈等参数才可以使用. 调节这些参数配合需要专业的知识, 设计一套方案使得调用者只要简单的设置就能够使用.

2.2 方案

1. UML图

   

3. 总结

4. 附录

4.1 例子代码:

1. python:

   Facade.py:

   # coding: utf-8"""    Example of  Facade pattern.    @author: Liu Weijie    @data: 2015-12-15    需求:        设计一个傻瓜相机, 只要选好拍照模式(白天模式或夜间模式), 即可自动完成各参数的设定."""class FlashLight(object):    """ SubSystem1 """    def __init__(self, is_open_in=False):        self.is_open = is_open_in    def open(self):        self.is_open = True    def close(self):        self.is_open = Falseclass Shutter(object):    """ SubSystem2 """    def action(self):        print "action!"class Focus(object):    """ SubSystem3 """    def __init__(self, value_in=0):        self.focue_value = value_in    def set_focus_value(self, value):        self.focue_value = valueclass Aperture(object):    """ SubSystem4 """    def __init__(self, value_in=0):        self.aperture_value = value_in    def set_aperture_value(self, value):        self.aperture_value = valueclass Camera(object):    """ Facade """    def __init__(self):        self.flash_light = FlashLight()        self.shutter = Shutter()        self.focus = Focus()        self.aperture = Aperture()    def set_day_mode(self):        self.flash_light.close()        self.focus.set_focus_value(10)        self.aperture.set_aperture_value(10)        print "set to day model successfuly!"    def set_night_mode(self):        self.flash_light.open()        self.focus.set_focus_value(50)        self.aperture.set_aperture_value(80)        print "set to night model successfuly!"    def action(self):        self.shutter.action()if __name__ == "__main__":    camera = Camera()    camera.set_day_mode()    camera.action()    camera.set_night_mode()    camera.action()

2. cpp

   main.cpp:

   /*Example of  Facade pattern.@author: Liu Weijie@data: 2015-12-15需求:    设计一个傻瓜相机, 只要选好拍照模式(白天模式或夜间模式), 即可自动完成各参数的设定.*/#include <iostream>// SubSystem1class FlashLight{public:    FlashLight(bool is_open_in=false){        is_open = is_open_in;    }    void open(){        is_open = true;    }    void close(){        is_open = false;    }private:    bool is_open;};// SubSystem2class Shutter{public:    void action(){        std::cout<<"action!\n";    }};// SubSystem3class Focus{public:    void set_focus_value(int value_in){        focus_value = value_in;    }private:    int focus_value;};// SubSystem4class Aperture{public:    Aperture(int value_in=0){        aperture_value = value_in;    };    void set_aperture_value(int value_in){        aperture_value =value_in;    };private:    int aperture_value;};// Facadeclass Camera{public:    Camera(){        std::cout<<"create a camera successfully!\n";    }    void set_day_mode(){        flash_light->close();        focus->set_focus_value(10);        aperture->set_aperture_value(10);        std:: cout<<"set to day mode!";    }    void set_night_mode(){        flash_light->close();        focus->set_focus_value(10);        aperture->set_aperture_value(90);        std:: cout<<"set to night mode!";    }    void action(){        shutter->action();    }private:    FlashLight* flash_light = new FlashLight();    Shutter* shutter = new Shutter();    Focus* focus = new Focus();    Aperture* aperture = new Aperture();};int main(int argc, const char * argv[]) {    Camera* new_camera = new Camera();    new_camera->set_day_mode();    new_camera->action();    new_camera->set_night_mode();    return 0;}