Property value about kefir

[rpominov]

No, there is no way to get current value of property.
If you really need to, you can do something like this:

var notSet = {};
var value = notSet;
var setVal = function(x) {value = x};
obs.onValue(setVal).offValue(setVal);
if (value === notSet) {
  // property has no current value yet
} else {
  // here it is, current value in the `value` variable
}

But don't use ._current it may contain internal special value, or be outdated (updates on activation).

To check if an observable a property, just do obs instanceof Kefir.Property

[iofjuupasli]

It looks like dirty solution. Also it's not clear that onValue on Property calls handler synchronously (and will be sync in future).
Is it possible to add this method to api (getCurrent)? Seems like it's very easy to add now.
Property - is smth that contains value. Do I understand correctly? So, there is value, but we can't get it. A little curiously.

[rpominov]

It looks dirty because it not right thing to do. It not very easy to add such method to the API, but possible (using a hack like one above). But I don't think that method should be in API (I agree with Bacon.js on this https://github.com/baconjs/bacon.js/wiki/FAQ#how-do-i-get-the-latest-value-of-a-property)

[rpominov]

A little more inside on the subject.

As I mentioned before, ._current not always contain current value of a property. It might be outdated and gets updated when you add first subscriber. So first (and all the rest) subscribers always gets correct current value.

This works that way to make possible get current value from any source. For example one can do something like this:

var inputValue = Kefir.fromBinder(function(emitter) {

  // the current value of the property will come from this line
  emitter.emit($input.val()); 

  function emitVal() {emitter.emit($input.val())}
  $input.on('change', emitVal);
  return function() {
    $input.off('change', emitVal);
  }
}).toProperty();

I can't remember now, but there is also another reasons why it works that way. Mostly it important on some edge cases. In early versions of Kefir there was method .getCurrent(), and it was used internally in all places where one observable subscribes to another, but it didn't go well.

Closing it now, I hope I answered your question :)