Question

我有以下单身人士

arr_hsh.max_by { |h| h['score'] }
#=> {:name=>"Outdoor", :game_code=>"C5", :score=>"61.68"}

每次我呼叫class WebSocketSingleton { IOWebSocketChannel _channel; WebSocketSingleton._privateConstructor(); static final WebSocketSingleton _instance = WebSocketSingleton._privateConstructor(); static WebSocketSingleton get instance => _instance; IOWebSocketChannel get channel{ if(_channel == null){ debugPrint("Creating new channel"); _channel = IOWebSocketChannel.connect( "wss://42zn68xb57.execute-api.us-east-1.amazonaws.com/Test"); } return _channel; } }时，它都会创建一个WebSocketSingleton.instance的新实例。

问题：

IOWebSocketChannel是否应该返回先前创建的WebSocketSingleton实例，而不是每次调用IOWebSocketChannel都创建一个新实例？

Answer 1

我认为您的IOWebSocketChannel.connect中存在一些无法创建实例的问题。

这是与您类似的代码，除了在创建新实例时使用默认构造函数，并且“创建新通道”仅打印一次。

class Channel {}

class Singleton {
  Singleton._();

  static final Singleton _instance = Singleton._();

  static Singleton get instance => _instance;

  Channel _channel;

  Channel get channel {
    if (_channel == null) {
      print("Creating new channel");
      _channel = Channel();
    }

    return _channel;
  }
}


void main() {
  Singleton.instance.channel;
  Singleton.instance.channel;
}

Answer 2

我认为连接方法存在一些问题，我认为它是静态的，我通过创建类的对象来调用connect，并且它仅作为创建单个实例的原因而工作。

void main() {
  WebSocketSingleton.instance.channel;
  WebSocketSingleton.instance.channel;
  WebSocketSingleton.instance.channel;
}



class WebSocketSingleton {

  IOWebSocketChannel _channel;

  WebSocketSingleton._privateConstructor();

  static final WebSocketSingleton _instance = WebSocketSingleton._privateConstructor();

  static WebSocketSingleton get instance => _instance;

  IOWebSocketChannel get channel{
    if(_channel == null){
      debugPrint("Creating new channel");
      _channel =  IOWebSocketChannel().connect(
          "wss://42zn68xb57.execute-api.us-east-1.amazonaws.com/Test");
    }

    return _channel;
  }
}

class IOWebSocketChannel {
  IOWebSocketChannel connect(String url) {
    return this;
  }
}

颤振中的单例模式

2 个答案: