Golang语言情怀-第27期 Go 语言设计模式 命令

type command interface {
    execute()
}

//开灯命令
type lightOnCommand struct {
    mLight *light //命令对象包含的特定接收者
}

//返回一个开灯命令的实例对象
func NewLightOnCommand(light *light) command {
    return &lightOnCommand{mLight: light}
}

//实现接口方法捆绑接收者的动作
func (this *lightOnCommand) execute() {
    if !this.mLight.isOn() {
        this.mLight.setOn(true) //开灯
    }
}

//关灯命令
type lightOffCommand struct {
    mLight *light
}

func NewLightOffCommand(light *light) command {
    return &lightOffCommand{mLight: light}
}

func (this *lightOffCommand) execute() {
    if this.mLight.isOn() {
        this.mLight.setOn(false) //关灯
    }
}

type receiver interface {
    setOn(bool) //true：开/false：关
    isOn() bool
}

//打开命令                                                 
type onCommand struct {
    receiver Receiver
}

//创建打开命令的实例，为该实例捆绑接收者                          
func NewOnCommand(receiver Receiver) command {
    return &onCommand{receiver}
}

//被封装的“请求”                                          
func (this *onCommand) execute() {
    if !this.receiver.isOn() {
        this.receiver.setOn(true) //打开
    }
}

//关闭命令                                           
type offCommand struct {
    receiver Receiver
}

func NewOffCommand(receiver Receiver) command {
    return &offCommand{receiver}
}

func (this *offCommand) execute() {
    if !this.receiver.isOn() {
        this.receiver.setOn(false) //关闭
    }
}

type RemoteController struct {
    slot command
}

func (this *RemoteController) SetCommand(command command) {
    this.slot = command
}

func (this *RemoteController) ButtonPressed() {
    if this.slot == nil {
        panic("Do not assign command to Controller's slot!")
    }
    this.slot.execute()
}

const (
    LIGHT = " light"
    DOOR  = " door"
)

//接收者接口        
type Receiver interface {
    setOn(bool)
    isOn() bool
}

type light struct {
    name string
    on   bool
}

func (this *light) setOn(b bool) {
    if b {
        fmt.Println(this.name + LIGHT + " is on.")
    } else {
        fmt.Println(this.name + LIGHT + " is off.")
    }
    this.on = b
}

func (this *light) isOn() bool {
    return this.on
}

func NewRoomLight() Receiver {
    return &light{"Room", false}
}

func NewTableLampLight() Receiver {
    return &light{"Table Lamp", false}
}

type door struct {
    name string
    on   bool
}

func (this *door) setOn(b bool) {
    if b {
        fmt.Println(this.name + DOOR + " is opened.")
    } else {
        fmt.Println(this.name + DOOR + " is closed.")
    }
    this.on = b
}

func (this *door) isOn() bool {
    return this.on
}

func NewGarageDoor() Receiver {
    return &door{"Garage", false}
}

func NewKitchenDoor() Receiver {
    return &door{"Kitchen", false}
}

func main() {
        ctrl := new(command.RemoteController)
    var roomLight, garageDoor command.Receiver

    roomLight = command.NewRoomLight()
    garageDoor = command.NewGarageDoor()

    cmdOn := command.NewOnCommand(roomLight)
    cmdOff := command.NewOffCommand(garageDoor)

    ctrl.SetCommand(cmdOn)
    ctrl.ButtonPressed()
    ctrl.SetCommand(cmdOff)
    ctrl.ButtonPressed()
}