[英]Using emit function in node.js
I can't figure out why I can't make my server to run emit function. 我不知道为什么我不能让我的服务器运行发射功能。
Here's my code: 这是我的代码:
myServer.prototype = new events.EventEmitter;
function myServer(map, port, server) {
...
this.start = function () {
console.log("here");
this.server.listen(port, function () {
console.log(counterLock);
console.log("here-2");
this.emit('start');
this.isStarted = true;
});
}
listener HERE...
}
The listener is: 侦听器是:
this.on('start',function(){
console.log("wtf");
});
All the console types is this: 所有控制台类型是这样的:
here
here-2
Any idea why it wont print 'wtf'
? 知道为什么它不会打印
'wtf'
吗?
Well, we're missing some code, but I'm pretty sure this
in the listen
callback won't be your myServer
object. 好了,我们缺少一些代码,但我敢肯定,
this
在listen
回调不会是你myServer
的对象。
You should cache a reference to it outside the callback, and use that reference... 您应该在回调之外缓存对它的引用,并使用该引用...
function myServer(map, port, server) {
this.start = function () {
console.log("here");
var my_serv = this; // reference your myServer object
this.server.listen(port, function () {
console.log(counterLock);
console.log("here-2");
my_serv.emit('start'); // and use it here
my_serv.isStarted = true;
});
}
this.on('start',function(){
console.log("wtf");
});
}
...or bind
the outer this
value to the callback... ...或
bind
外部this
值bind
到回调...
function myServer(map, port, server) {
this.start = function () {
console.log("here");
this.server.listen(port, function () {
console.log(counterLock);
console.log("here-2");
this.emit('start');
this.isStarted = true;
}.bind( this )); // bind your myServer object to "this" in the callback
};
this.on('start',function(){
console.log("wtf");
});
}
For new people, make sure to you use the ES6 arrow function whenever you can to bind the context of "this" to your function. 对于新手,请确保在可以将“ this”的上下文绑定到函数时使用ES6 箭头函数。
// Automatically bind the context
function() {
}
() => {
}
// You can remove () when there is only one arg
function(arg) {
}
arg => {
}
// inline Arrow function doesn't need { }
// and will automatically return
function(nb) {
return nb * 2;
}
(nb) => nb * 2;
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