Command 패턴

참고 자료_ 정의

정의

나중에 실행시킬 이벤트를 캡슐화시킨 객체를 만드는 행위 디자인 패턴

• command: receiver를 알고 있고, receveir의 method를 실행시킴. receveier 메서드에 전달할 인자 가짐. execute() 가짐
• receiver: execute() 호출 시 동작
• invoker: ex. command.execute()
• client: 어느 시점에 어떤 command를 호출할지 결정 ex. HomeManager 메서드들

참고 자료_ MVVM
MVVM 패턴은 Command 패턴과 Data Binding 두 가지 패턴을 사용하여 구현되었습니다.
Command 패턴과 Data Binding을 이용하여 View와 View Model 사이의 의존성을 없앴습니다.

UML

예제 코드1

참고자료 _ 예제코드

protocol Command {//command
    func execute()
}

class Home {
    func lockDoor() {
        print("lock the door")
    }
    
    func unlockDoor() {
        print("unlock the door")
    }
    
    func openGarage() {
        print("open the garage")
    }
    
    func closeGarage() {
        print("close the garage")
    }
}

class LockDoorCommand: Command {//concrete command
    private let home: Home
    
    init(home: Home) {
        self.home = home
    }
    
    func execute() {
        home.lockDoor()
    }
}

class UnLockDoorCommand: Command {
    private let home: Home
    
    init(home: Home) {
        self.home = home
    }
    
    func execute() {
        home.unlockDoor()
    }
}

class OpenGarageCommand: Command {
    private let home: Home
    
    init(home: Home) {
        self.home = home
    }
    
    func execute() {
        home.openGarage()
    }
}

class CloseGarageCommand: Command {
    private let home: Home
    
    init(home: Home) {
        self.home = home
    }
    
    func execute() {
        home.closeGarage()
    }
}

class HomeManager { //Invoker
    private let lockDoorCommand: Command
    private let unlockDoorCommand: Command
    private let openGarageCommand: Command
    private let closeGarageCommand: Command
    
    init(home: Home) {
        lockDoorCommand = LockDoorCommand(home: home)
        unlockDoorCommand = UnLockDoorCommand(home: home)
        openGarageCommand = OpenGarageCommand(home: home)
        closeGarageCommand = CloseGarageCommand(home: home)
    }
    
    func secure() {
        lockDoorCommand.execute()
        closeGarageCommand.execute()
    }
    
    func open() {
        unlockDoorCommand.execute()
        openGarageCommand.execute()
    }
}

let manager = HomeManager(home: Home())

manager.open()
manager.secure()

/*
 unlock the door
 open the garage
 lock the door
 close the garage
 */

예제 코드2

참고 자료_ 에제 코드

// 실행 기능 추상화 -> 여러 기능 수행하도록 캡슐화
protocol Command {
    func execute()
}

class Button {
    private var command: Command

    init(command: Command) {
        self.command = command
    }

    func setCommand(command: Command) {
        self.command = command
    }

    func pressed() {
        self.command.execute()
    }

}

class Lamp {
    func turnOn() {
        print("Lamp On")
    }
}

class LampOnCommand: Command {
    private var lamp: Lamp

    init(lamp: Lamp) {
        self.lamp = lamp
    }

    func execute() {
        self.lamp.turnOn()
    }

}

class Alarm {
    func start() {
        print("Alarm Start")
    }
}

class AlarmStartCommand: Command {
    private var alarm: Alarm

    init(alarm: Alarm) {
        self.alarm = alarm
    }

    func execute() {
        self.alarm.start()
    }
}

//client
let lampOnCommand = LampOnCommand(lamp: Lamp())
let alarmStartCommand = AlarmStartCommand(alarm: Alarm())

// 램프를 켜는 버튼
let button1 = Button(command: lampOnCommand)
button1.pressed()                               // Lamp On

// 한 번 누르면 알람이 켜지고 두 번 누르면 램프가 켜지는 버튼
let button2 = Button(command: alarmStartCommand)
button2.pressed()                               // Alarm Start
button2.setCommand(command: lampOnCommand)
button2.pressed()                               // Lamp On