为什么我无法在订阅中调用方法 - 无法读取未定义的属性“showMessageFromSocket”

Question

我想在订阅块中调用方法，但我得到“无法读取未定义的属性‘showMessageFromSocket’”。如何调用 showMessageFromSocket 方法？从角度来看这是可能的。export default class ConnectedChatroom extends Component<  ConnectedChatroomProps,  ConnectedChatroomState> {  wsObj: CompatClient;  constructor(props: Props, context: *) {    super(props, context);    this.configureSocketChannel('dassfa')  }  showMessageFromSocket(message)  {    console.log(message);    //do something  }  configureSocketChannel(senderId: string) {    let ws = Stomp.client("ws://localhost:8080/chat");    ws.connect({}, function (frame) {      ws.subscribe("/topic/messages", function (message) {        this.showMessageFromSocket(message);      });    }, function (error) {      console.log("STOMP error " + error);    });    this.wsObj = ws;  }

Answer 1

使用arrow函数来访问类成员，例如没有自变量的类的变量或方法。

尝试像下面这样

configureSocketChannel(senderId: string) {

    let ws = Stomp.client("ws://localhost:8080/chat");

    ws.connect({},  (frame) => {

      ws.subscribe("/topic/messages",  (message) => {

        this.showMessageFromSocket(message);

      });

    }, function (error) {

      console.log("STOMP error " + error);

    });

    this.wsObj = ws;

}