command模式（c语言实现）

2014年写过一篇实现，重读一遍《设计模式》，参考网上的一篇文章，又重新写了一遍。

我体会到，c++的类在c语言里面用struct代替之后，c++的this指针可以通过传入struct本身的指针来完成。

而在command模式里的Command实际上既包含了对象（pData），又包含了命令接口（exe）。

#include <stdio.h>
#include <stdlib.h>
#include <cassert>

#define COMMAND_SLOT_MAX (2)
typedef struct _Command
{
    void* pData;
    void (*exe)(struct _Command* pCommand);
}Command;

typedef struct _RemoteControl
{
    Command onCommands[COMMAND_SLOT_MAX];
    Command offCommands[COMMAND_SLOT_MAX];
    void (*setCommand)(int slot, Command onCommand, Command offCommand, struct _RemoteControl *pRemoteControl);
    void (*onButtonWasPushed)(int slot, struct _RemoteControl *pRemoteControl);
    void (*offButtonWasPushed)(int slot, struct _RemoteControl *pRemoteControl);
}RemoteControl;
 
void setCommand(int slot, Command onCommand, Command offCommand, struct _RemoteControl *pRemoteControl)
{
    assert(NULL != pRemoteControl);
    assert(slot < COMMAND_SLOT_MAX);
    pRemoteControl->onCommands[slot] = onCommand;
    pRemoteControl->offCommands[slot] = offCommand;
    return;
}

void onButtonWasPushed(int slot, struct _RemoteControl *pRemoteControl)
{
    assert(NULL != pRemoteControl);
    assert(slot < COMMAND_SLOT_MAX);
    pRemoteControl->onCommands[slot].exe(&pRemoteControl->onCommands[slot]);
    return;
}

void offButtonWasPushed(int slot, struct _RemoteControl *pRemoteControl)
{
    assert(NULL != pRemoteControl);
    assert(slot < COMMAND_SLOT_MAX);
    pRemoteControl->offCommands[slot].exe(&pRemoteControl->offCommands[slot]);
    return;
}

//light device
typedef struct _Light
{
    void (*on)(struct _Light* pLight);   
    void (*off)(struct _Light* pLight);   
}Light;

void light_on_command(struct _Command* pCommand)
{
    assert(NULL != pCommand);
    ((Light*)(pCommand->pData))->on((Light*)(pCommand->pData));
    return;
}

void light_off_command(struct _Command* pCommand)
{
    assert(NULL != pCommand);
    ((Light*)(pCommand->pData))->off((Light*)(pCommand->pData));
    return;
}

void light_on(struct _Light* pLight)
{
    printf("light is on!\n");
}
void light_off(struct _Light* pLight)
{
    printf("light is off!\n");
}

//radio device
typedef struct _Radio
{
    void (*on)(struct _Radio* pLight);   
    void (*off)(struct _Radio* pLight);   
}Radio;

void radio_on_command(struct _Command* pCommand)
{
    assert(NULL != pCommand);
    ((Radio*)(pCommand->pData))->on((Radio*)(pCommand->pData));
    return;
}

void radio_off_command(struct _Command* pCommand)
{
    assert(NULL != pCommand);
    ((Radio*)(pCommand->pData))->off((Radio*)(pCommand->pData));
    return;
}

void radio_on(struct _Radio* pRadio)
{
    printf("Radio is on!\n");
}
void radio_off(struct _Radio* pRadio)
{
    printf("Radio is off!\n");
}

int main()
{
    Light light;
    light.on = light_on;
    light.off = light_off;

    Command light_on_cmd;
    light_on_cmd.pData = &light;
    light_on_cmd.exe = light_on_command;

    Command light_off_cmd;
    light_off_cmd.pData = &light;
    light_off_cmd.exe = light_off_command;

    Radio radio;
    radio.on = radio_on;
    radio.off = radio_off;

    Command radio_on_cmd;
    radio_on_cmd.pData = &radio;
    radio_on_cmd.exe = radio_on_command;

    Command radio_off_cmd;
    radio_off_cmd.pData = &radio;
    radio_off_cmd.exe = radio_off_command;

    RemoteControl remotecontrol;
    remotecontrol.setCommand = setCommand;
    remotecontrol.onButtonWasPushed = onButtonWasPushed;
    remotecontrol.offButtonWasPushed = offButtonWasPushed;
    remotecontrol.setCommand(0, light_on_cmd, light_off_cmd, &remotecontrol);
    remotecontrol.setCommand(1, radio_on_cmd, radio_off_cmd, &remotecontrol);

    remotecontrol.onButtonWasPushed(0, &remotecontrol);
    remotecontrol.onButtonWasPushed(1, &remotecontrol);
    remotecontrol.offButtonWasPushed(0, &remotecontrol);
    remotecontrol.offButtonWasPushed(1, &remotecontrol);

    return 0;
}

参考文章：https://blog.csdn.net/feixiaoxing/article/details/7184325

以前写的文章：https://blog.csdn.net/hope_worker/article/details/23949593