Add Events#listenToOnce

[gsamokovarov]

As per discussion in #2045, I implemented oneTimeListenTo, an inversion-of-control version of once. @caseywebdev and @tgriesser voted for the name listenToOnce, but I went with oneTimeListenTo as it sounds clearer to me, but its up for discussion. If you guys like listenToOnce or some other name, I can change it.

Edit:

Changed the name from oneTimeListenTo to onceListenTo. Its still up for discussion, though.

Edit:

Changed to listenToOnce as per the comments.

[philfreo]

I'd prefer listenToOnce (or even onceListenTo) so it parallels once, rather than using "oneTime"

[AjaxSolutions]

Using 'once' in the method name is more consistent and shorter.

[tbranyen]

Here we go again with a thread about naming, but I'd prefer listenToOnce :-p

[gsamokovarov]

Fair enough. I like onceListenTo its easier to type and it keeps the once reference in there.

[tgriesser]

I'm with @tbranyen and @philfreo on listenToOnce

[gsamokovarov]

I still kinda want to keep the to at the end. Its consistent with how listenTo reads in code. But if most of you like listenToOnce, so be it 😄

[akre54]

also pitching in with @tbranyen and @philfreo. I think the semantics of listenToOnce aren't that awkward (or are at least much less awkward than onceListenTo)

[gsamokovarov]

Have to agree with you. onceListenTo sounds kind of ambiguous. Will wait for the other guys to chime in before amending the last commit.

[caseywebdev]

👍 listenToOnce

[eastridge]

+1 listenToOnce

[gsamokovarov]

listenToOnce it is 😄

[philfreo]

👍 on this (or some other way to easily clean up once events)

[Yahasana]

listenOnce 💯

[caseywebdev]

It needs the To to imply the first argument 😉

[grydstedt]

+1 listenToOnce!

[gsamokovarov]

Rebased this one, so it can be applied cleanly to the current tree.

[tgriesser]

@jashkenas - any opinion on this one? It does make the Event listeners symmetrical...

[jashkenas]

Fun implementation and nice API symmetry, but I'm a little concerned if anyone will actually find it useful. Would y'all use this?

[philfreo]

@jashkenas yes -- with listenTo now it's much more rare for me to have to manually cleanup listeners in View#remove now. But there's no automatic way to do that with once events (which I do use), and this fixes that

[dgbeck]

I have not yet found occation for "once" events. A chained interaction perhaps where the second part depends on first, like choosing item from popup menu?

[akre54]

I have once in a number of places where I want the callback removed after the event has been triggered, before the once event was introduced, I had at least a dozen places in code with code like

foo.on('closePopup', function() {
  doSomething();
  foo.off('closePopup')
});

a listenToOnce event would be a great help for me.

[tbranyen]

Found myself needing this today:

this.listenToOnce(this.filters, "change", function() {
  this.filters.add(new Filter.Model());
});

I don't want to add a new filter every single time one has changed, I only ever add one once.

[ricogallo]

@jashkenas I'm going to use this like that:

this.listenToOnce(this.model, signedEvent, function() {
  // do stuff;
});

👍