A really silly-novice question about events

[q2dg2b]

Hello friends

I don't know why this code doesn't work:

var source = new (require("events").EventEmitter)()

var sink = new (require("events").EventEmitter)()
setInterval(function() {source.emit("radiation")}, 1000)
sink.on("radiation", function(){console.log("¡Detected!")})

However, this code does work:

var source = new (require("events").EventEmitter)()
setInterval(function() {source.emit("radiation")}, 1000)
source.on("radiation", function(){console.log("¡Detected!")})

Isn't possible to emit an event by an object and to receive this event by another object, then?

Thanks!!

[zladuric]

The keyword here is 'on' method. source.on vs sink.on. On is eventemitter method that listens to events emited on THAT object.

So if you emit stuff from source, attaching a listener to sink does not help. It doesn't matter what kind of object your sink is - it did not emit any radiation.

To make one object emit events and have others listen, you have two simple routes. One is to get attached to source from all your listeners, or the other is to use some kind of a bus or pubsub.

For the first version, your source would be an EventEmitter and it would emit('radiation'). And your sink can be any other object (including an event emiter), which has a listener.

Something like this:

var Sink =  new (require("events").EventEmitter)() /* or whatever else */

Sink.radiationHandler = function(){

    console.log('run to the hills!');

}

var sink = new Sink;

Then you attach that method as a listener to it, like this:

source.on('radiation', sink.radiationHandler);

The other method I've described is a pubsub, kind of like this:

https://gist.github.com/fatihacet/1290216

[Angel Java Lopez]

The line

sink.on("radiation", function(){console.log("¡Detected!")})

says: "when sink object emit radiation event, do something"

But your event emitter is the source object.

So, to take an event from source, and act on sink, you must write something like

source.on("radiation", function () { sink.dosomething() });

Angel "Java" Lopez

@ajlopez

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[Gagle]

El jueves, 6 de febrero de 2014 00:45:47 UTC+1, q2dg2b escribió:

Hello friends

Isn't possible to emit an event by an object and to receive this event by another object, then?

Thanks!!

Nope

[Angel Java Lopez]

A refinement

source.on("radiation", function (dataradiation) { sink.process(dataradiation) });

could be written as

source.on("radiation", sink.process);

[q2dg2b]

Ook! Thanks a lot!!

[q2dg2b .]

Ahá...very interesting!! Thanks a lot!!

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