lwc -如何从lwc回调中调用函数

Question

未能将此挑战与文档协调:/希望有人能向我指出为什么当这个lwc呈现(成功)并通过其empApi订阅接收一个事件时，它抛出一个'handleGoNext未定义‘运行时错误。我知道这个函数是不可见的，但是我不能构造这样的东西，这样就可以成功地进行函数调用。调用this.handleGoNext()也不起作用。任何指点都将不胜感激！

handleGoNext(){
    // *** this is the logic Im hoping to call ***
};


// Initializes the component
connectedCallback() {
   if(this.subscription = {}){ 
        
        // Callback invoked whenever a new event message is received
        
        const messageCallback = function (response) {
            handleGoNext(); // *** THIS IS THE CALL THAT BREAKS THINGS ***
        };
        
        // Invoke subscribe method of empApi. Pass reference to messageCallback
        subscribe(this.channelName, -1, messageCallback).then((response) => {
            // Response contains the subscription information on subscribe call
            console.log(
                'Subscription request sent to: ',
                JSON.stringify(response.channel)
            );
            this.subscription = response;
        });
    }
}

Answer 1

当你做subscribe(this.channelName, -1, this.handleGoNext)时会发生什么

这是我在复活节前后的功能，最近没有检查它是否仍然有效。

isSubscribed = false;
subscription = {};
replayId;

@track data = [];

subscribe(id) {
        const handleMessage = (response) => {
            let val = Object.assign({}, response.data.event, response.data.payload);
            this.replayId = Math.max(this.replayId ?? 0, val.replayId);

            /*  do not use this.data.push(val);
                it doesn't play well with datatable. Use the spread operator or JSON.parse/JSON.stringify trick.
                Plus we want new rows to be added on top of the list.`
            */
            this.data = [val, ...this.data];
        };

        subscribe(this.channel, id, handleMessage).then((response) => {
            this.subscription = response;
            this.isSubscribed = true;
        });
    }