Successor for Bacon.fromBinder

[raimohanska]

In #703 it was suggested that this version of Bacon.fromEvent should be added:

Bacon.fromEvent(
    (listener) => window.addEventListener('scroll', listener, {passive: true}),
    (listener) => window.removeEventListener('scroll', listener, {passive: true}),
    () => window.scrollX
);

It has the virtue of being more readable than Bacon.fromBinder. From my point of view, it also looks like it should be returning a Property because the third function argument is used to get a current value. The initial value of the Property could be set at the time of creation by calling the third function.

[semmel]

Ehm isn't that pull request about

Bacon.fromEvent(window, 'scroll', { passive: true }, event => event.prop)

I mean about Bacon.fromEvent and not Bacon.fromBinder?
I find Bacon.fromBinder as general adapter just fine the way it is.

[raimohanska]

Ysh

[raimohanska]

Oops sorry

[raimohanska]

Yeah there was this suggestion in the comments

[steve-taylor]

Given the symmetry of bind/unbind calls, how about something like this to avoid duplication:

Bacon.fromEventBinder(
    window,
    (binder, listener) => binder('scroll', listener, {passive: true}),
    () => window.scrollX
);

The second parameter is called with window.addEventListener.bind(window) and, on closing the stream, window.removeEventListener.bind(window).

Edit: This could just be an alternative way of calling Bacon.fromEvent. This would get around some of the future-proofing issues discussed in #703:

• Bacon.fromEvent(EventTarget|EventEmitter, String [, Function]) (current signature)
• Bacon.fromEvent(EventTarget|EventEmitter, Function [, Function]) (alternative signature)

The key is the 2nd parameter. If it's a string, Bacon.fromEvent works exactly as it does now. If it's a function, the function is used to bind/unbind the listener to/from the target.

So

Bacon.fromEvent(window, 'scroll')

is equivalent to

Bacon.fromEventBinder(window, (binder, listener) => binder('scroll', listener));

(and eventTransformer can optionally be added to either of these).

[steve-taylor]

I find Bacon.fromBinder as general adapter just fine the way it is.

Agreed. There will always be use cases for Bacon.fromBinder in its current form that don't involve EventTargets or EventEmitters.

[steve-taylor]

I'll create a new PR shortly for the following:

Bacon.fromEvent(
    target: EventTarget|EventEmitter,
    eventSource: string|Function,
    eventTransformer?: Function
)

It will be an alternative to #703.

[steve-taylor]

See #710 and related documentation

[steve-taylor]

Might as well close this now that #710 is merged.