Golang命令模式封装请求实现教程

<span style="color: #008000">// 接收者：电灯</span>
type Light struct{}

func (l *Light) On() {
    fmt.Println("电灯已打开")
}

func (l *Light) Off() {
    fmt.Println("电灯已关闭")
}

<span style="color: #008000">// 命令接口</span>
type Command interface {
    Execute()
}

<span style="color: #008000">// 具体命令：开灯命令</span>
type LightOnCommand struct {
    light *Light
}

func (c *LightOnCommand) Execute() {
    c.light.On()
}

<span style="color: #008000">// 具体命令：关灯命令</span>
type LightOffCommand struct {
    light *Light
}

func (c *LightOffCommand) Execute() {
    c.light.Off()
}

<span style="color: #008000">// 调用者：遥控器</span>
type RemoteControl struct {
    command Command
}

func (r *RemoteControl) PressButton() {
    r.command.Execute()
}

func main() {
    light := &Light{}
    onCommand := &LightOnCommand{light: light}
    offCommand := &LightOffCommand{light: light}

    remote := &RemoteControl{}

    remote.command = onCommand
    remote.PressButton() // 输出：电灯已打开

    remote.command = offCommand
    remote.PressButton() // 输出：电灯已关闭
}

<span style="color: #008000">// 扩展命令接口支持撤销</span>
type UndoableCommand interface {
    Command
    Undo()
}

func (c *LightOnCommand) Undo() {
    c.light.Off()
}

func (c *LightOffCommand) Undo() {
    c.light.On()
}

type RemoteControlWithUndo struct {
    command Command
    history []UndoableCommand
}

func (r *RemoteControlWithUndo) PressButton() {
    if cmd, ok := r.command.(UndoableCommand); ok {
        cmd.Execute()
        r.history = append(r.history, cmd)
    }
}

func (r *RemoteControlWithUndo) Undo() {
    if len(r.history) == 0 {
        return
    }
    last := r.history[len(r.history)-1]
    last.Undo()
    r.history = r.history[:len(r.history)-1]
}