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[英]Trying to expect a call to a function inside an anonymous function with JEST
[英]call react function inside anonymous function
我在這樣的反應組件中有一個函數
addItem: function(data) {
console.log(data)
var oldMessages = this.state.messages;
oldMessages.push({id: data.uid, content: data});
this.setState({messages: oldMessages});
this.scrollAndSetTimestamps()
this.updateCount()
},
componentDidMount: function() {
this.loadLatestMessages();
var socket = new SockJS('http://127.0.0.1:8080/stomp');
var stompClient = Stomp.over(socket);
stompClient.connect({}, function(frame) {
// subscribe to the /room.uid endpoint
stompClient.subscribe("/room.1247016", function(data) {
var message = data.body;
console.log("Received: "+message);
this.addItem();
});
});
},
事實證明,當消息到達時,找不到addItem
。 如何在anon函數中調用react方法?
最簡單的解決方案是在某個變量中存儲this
上下文的正確引用:
var self = this;
stompClient.connect({}, function(frame) {
stompClient.subscribe("/room.1247016", function(data) {
var message = data.body;
self.addItem();
});
});
您也可以使用Function.prototype.bind ,但這不是很易讀:
stompClient.connect({}, function(frame) {
stompClient.subscribe("/room.1247016", function(data) {
var message = data.body;
this.addItem();
}.bind(this));
}.bind(this));
最后,您還可以使用具有詞法范圍的ES2015 箭頭函數 :
stompClient.connect({}, frame => {
stompClient.subscribe("/room.1247016", data => {
var message = data.body;
this.addItem();
});
});
我無法真正測試你的代碼,但我認為這是因為js范圍。 在你調用addItem的地方,“this”不再指向組件,而是指向它的對象。 所以,你要修復它,一個引用方法是緩解范圍,代碼如下:
componentDidMount: function() {
var _self = this;
_self.loadLatestMessages();
var socket = new SockJS('http://127.0.0.1:8080/stomp');
var stompClient = Stomp.over(socket);
stompClient.connect({}, function(frame) {
// subscribe to the /room.uid endpoint
stompClient.subscribe("/room.1247016", function(data) {
var message = data.body;
console.log("Received: "+message);
_self.addItem();
});
});
},
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