命令模式

将Command作为一个抽象类（或者接口），而非一个函数

支持统一的Execute和Undo

example


public abstract class Command {
		public virtual void Execute(GameActor actor);
		public virtual void Undo(GameActor actor);
}

public class JumpCommand: Command {
		public override void Execute (GameActor actor) {
				actor.jump();
		}
		// Undo 略 
}

实际处理


public class InputHandler : SingletonMono<InputHandler>{
	
		public Command HandleInput() {
		if (isPressed(BUTTON_X)) return buttonX;
		  if (isPressed(BUTTON_Y)) return buttonY;
		  if (isPressed(BUTTON_A)) return buttonA;
		  if (isPressed(BUTTON_B)) return buttonB;
		
		  // 没有按下任何按键，就什么也不做
		  return NULL;
		}
		
		private Command buttonX;
		private Command buttonY;
		private Command buttonA;
		private Command buttonB;
		// Initialize
}


// Call
Command* command = InputHandler.GetInstance().HandleInput();
if (command is not null) {
		command.Execute(actor);
}

Undo操作的支持：需要记录「Previous State」

用闭包替代一个类：


function makeMoveUnitCommand(unit, x, y) {
  var xBefore, yBefore;
  return {
    execute: function() {
      xBefore = unit.x();
      yBefore = unit.y();
      unit.moveTo(x, y);
    },
    undo: function() {
      unit.moveTo(xBefore, yBefore);
    }
  };
}