Encapsulates a request as an object, allowing parameterization, queuing, and undo.

Turns actions into first-class objects.

abstract class Command {
  void execute();
  void undo();
}

class Light {
  void on() => print('Light on');
  void off() => print('Light off');
}

class LightOnCommand implements Command {
  final Light _light;
  LightOnCommand(this._light);

  @override
  void execute() => _light.on();
  @override
  void undo() => _light.off();
}

class Remote {
  final List<Command> _history = [];

  void press(Command cmd) {
    cmd.execute();
    _history.add(cmd);
  }

  void undoLast() => _history.removeLast().undo();
}

// Usage
final remote = Remote();
remote.press(LightOnCommand(Light())); // Light on
remote.undoLast();                      // Light off