Headfirst设计模式的C++实现——命令模式(Command)

先看如果不用命令模式的实现：

light.h

 #ifndef _LIGHT_H_
 #define _LIGHT_H

 #include <iostream>

 class LIGHT {
 public:
     void on() { std::cout << "light is on" << std::endl; }
     void off() { std::cout << "light is off" << std::endl; }
 };

 #endif

tv.h

 #ifndef _TV_H_
 #define _TV_H_

 #include <iostream>

 class TV {
 public:
     void open() { std::cout << "TV is opened" << std::endl; }
     void close() { std::cout << "TV is closed" << std::endl; }
 };
 #endif

remote.h

 #ifndef _REMOTE_H_
 #define _REMOTE_H_

 #include <string>
 #include <iostream>
 #include "tv.h"
 #include "light.h"

 class REMOTE {
 public:
     void set(int slot, const std::string& device) {
         if ( slot < MAX_SLOT_NUM ) {
             all_device[slot] = device;
         }
     }

     void press_on_button(int slot) {
         if ( slot >= MAX_SLOT_NUM ) {
             return;
         }
         if ( all_device[slot] == "" ) {
             std::cout << "slot " << slot << " is empty" << std::endl;
         }
         else {
             if ( "TV" == all_device[slot] ) {
                 TV tv;
                 tv.open();
             }
             else if ( "LIGHT" == all_device[slot] ) {
                 LIGHT light;
                 light.on();
             }
             else {
                 std::cout << "invalid type" << std::endl;
             }
         }
     }

     void press_off_button(int slot) {
         if ( slot >= MAX_SLOT_NUM ) {
             return;
         }
         if ( all_device[slot] == "" ) {
             std::cout << "slot " << slot << " is empty" << std::endl;
         }
         else {
             if ( "TV" == all_device[slot] ) {
                 TV tv;
                 tv.close();
             }
             else if ( "LIGHT" == all_device[slot] ) {
                 LIGHT light;
                 light.off();
             }
             else {
                 std::cout << "invalid type" << std::endl;
             }

         }
     }
 private:
     const static int MAX_SLOT_NUM = ;
     std::string all_device[MAX_SLOT_NUM];
 };

 #endif

main.cpp

 #include "remote.h"
 int main() {
     REMOTE remote;
     remote.set(, "TV");
     remote.set(, "LIGHT");
     remote.press_on_button();
     remote.press_off_button();
     remote.press_on_button();
 }

再看看使用命令模式的实现

light.h和tv.h不变

command.h

 #ifndef _COMMAND_H_
 #define _COMMAND_H_

 class COMMAND {
 public:
     virtual void execute() = ;
 };

 #endif

light_on_command.h

 #ifndef _LIGHT_ON_COMMAND_H_
 #define _LIGHT_ON_COMMAND_H_

 #include "command.h"
 #include "light.h"

 class LIGHT_ON_COMMAND : public COMMAND {
 private:
     LIGHT &light;
 public:
     LIGHT_ON_COMMAND( LIGHT &_light ) : light(_light) {}
     void execute() { light.on(); }
 };

 #endif

light_off_command.h

 #ifndef _LIGHT_OFF_COMMAND_H_
 #define _LIGHT_OFF_COMMAND_H_

 #include "command.h"
 #include "light.h"

 class LIGHT_OFF_COMMAND : public COMMAND {
 private:
     LIGHT &light;
 public:
     LIGHT_OFF_COMMAND( LIGHT &_light ) : light(_light) {}
     void execute() { light.off(); }
 };

 #endif

tv_on_command.h

 #ifndef _TV_ON_COMMAND_H_
 #define _Tv_ON_COMMAND_H_

 #include "command.h"
 #include "tv.h"

 class TV_ON_COMMAND : public COMMAND {
 private:
     TV &tv;
 public:
     TV_ON_COMMAND( TV&_tv) : tv(_tv) {}
     void execute() { tv.open(); }
 };

 #endif

tv_off_command.h

 #ifndef _TV_OFF_COMMAND_H_
 #define _TV_OFF_COMMAND_H_

 #include "command.h"
 #include "tv.h"

 class TV_OFF_COMMAND : public COMMAND {
 private:
     TV &tv;
 public:
     TV_OFF_COMMAND( TV&_tv) : tv(_tv) {}
     void execute() { tv.close(); }
 };

 #endif

remote.h

 #ifndef _REMOTE_H_
 #define _REMOTE_H_

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

 class REMOTE {
 public:
     REMOTE() {
         for ( int i = ; i < MAX_SLOT_NUM; i++ ) {
             on_commands[i] = NULL;
             off_commands[i] = NULL;
         }
     }

     void set(int slot, COMMAND& on_command, COMMAND& off_command) {
         if ( slot < MAX_SLOT_NUM ) {
             on_commands[slot] = &on_command;
             off_commands[slot] = &off_command;
         }
     }

     void press_on_button(int slot) {
         if ( slot < MAX_SLOT_NUM ) {
             if ( NULL != on_commands[slot] ) {
                 on_commands[slot]->execute();
             }
             else {
                 std::cout << "slot " << slot << " is empty" << std::endl;
             }
         }
     }

     void press_off_button(int slot) {
         if ( slot < MAX_SLOT_NUM ) {
             if ( NULL != off_commands[slot] ) {
                 off_commands[slot]->execute();
             }
             else {
                 std::cout << "slot " << slot << " is empty" << std::endl;
             }
         }
     }
 private:
     const static int MAX_SLOT_NUM = ;
     COMMAND *on_commands[MAX_SLOT_NUM];
     COMMAND *off_commands[MAX_SLOT_NUM];
 };

 #endif

main.cpp

 #include "remote.h"
 #include "tv_on_command.h"
 #include "tv_off_command.h"
 #include "light_on_command.h"
 #include "light_off_command.h"

 int main() {
     REMOTE remote;

     TV tv;
     TV_ON_COMMAND tv_on_command(tv);
     TV_OFF_COMMAND tv_off_command(tv);
     remote.set(, tv_on_command, tv_off_command);

     LIGHT light;
     LIGHT_ON_COMMAND light_on_command(light);
     LIGHT_OFF_COMMAND light_off_command(light);
     remote.set(, light_on_command, light_off_command);

     remote.press_on_button();
     remote.press_off_button();
     remote.press_on_button();
 }