如何在as3中实现撤消和重做功能

// 定义一个基础命令类
class Command {
  public function execute():void {}
  public function undo():void {}
}

// 定义一个具体命令类，实现具体的操作和撤销操作
class MyCommand extends Command {
  private var _target:Object;
  private var _property:String;
  private var _oldValue:Object;
  private var _newValue:Object;

  public function MyCommand(target:Object, property:String, newValue:Object) {
    _target = target;
    _property = property;
    _oldValue = _target[property];
    _newValue = newValue;
  }

  override public function execute():void {
    _target[_property] = _newValue;
  }

  override public function undo():void {
    _target[_property] = _oldValue;
  }
}

// 定义一个命令堆栈
class CommandStack {
  private var _stack:Array = [];

  public function push(command:Command):void {
    _stack.push(command);
  }

  public function pop():Command {
    return _stack.pop();
  }

  public function get length():uint {
    return _stack.length;
  }
}

// 在实际应用中，可以通过以下方式使用命令模式实现撤销和重做功能：
var commandStack:CommandStack = new CommandStack();

// 执行操作并将其添加到堆栈中
var command:MyCommand = new MyCommand(someObject, "propertyName", newValue);
command.execute();
commandStack.push(command);

// 撤销操作
if (commandStack.length > 0) {
  var lastCommand:Command = commandStack.pop();
  lastCommand.undo();
}

// 重做操作
if (commandStack.length > 0) {
  var lastCommand:Command = commandStack.pop();
  lastCommand.execute();
  commandStack.push(lastCommand);
}