[英]Trying to expect a call to a function inside an anonymous function with JEST
[英]call react function inside anonymous function
我在这样的反应组件中有一个函数
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();
});
});
},
事实证明,当消息到达时,找不到addItem
。 如何在anon函数中调用react方法?
最简单的解决方案是在某个变量中存储this
上下文的正确引用:
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 ,但这不是很易读:
stompClient.connect({}, function(frame) {
stompClient.subscribe("/room.1247016", function(data) {
var message = data.body;
this.addItem();
}.bind(this));
}.bind(this));
最后,您还可以使用具有词法范围的ES2015 箭头函数 :
stompClient.connect({}, frame => {
stompClient.subscribe("/room.1247016", data => {
var message = data.body;
this.addItem();
});
});
我无法真正测试你的代码,但我认为这是因为js范围。 在你调用addItem的地方,“this”不再指向组件,而是指向它的对象。 所以,你要修复它,一个引用方法是缓解范围,代码如下:
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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