flutter命名构造函数和工厂构造函数

class Frame {
  final double x;
  final double y;
  final double width;
  final double height;
  const Frame.only({this.x, this.y, this.width, this.height});
  factory Frame(double x){
    return Frame.only(x:x);
  }
}

Frame(123.0);
Frame.only();