if:then:else operator: missing? about rxswift HOT 7 CLOSED

@iandundas I think you can also use combineLatest

combineLatest(ifSequence, thenSequence, elseSequence) { condition, thenElement, elseElement in
       if (condition) {
            return thenElement 
      }
      else {
            return elseElement
      }
}

If you really really need if:then:else, then you can just create your own operator that wraps combineLatest.

In that way you an create if:then:elseif:elseif ....:else or what ever imperative operator do you need applied easily :)

Hope this helps.

from rxswift.

If I understand you correctly then something like what I have on line 57 of this file should do it: https://github.com/dtartaglia/MVVMSwiftSample/blob/feature/make_reactive/MVVM/DetailViewController.swift

In short I think sampleLatest sounds like what you need. You might have to combine the parameter of sampleLatest with a filter.

from rxswift.

problem magically rearranges in head, combineLatest solution condenses into view
... okay that actually could work! Thanks both, I'll post back if still stuck. 👍🏻

from rxswift.

So, (if signal A's events are allowed through only if signal B evaluates to true, described above), what would you return if you didn't want anything to be passed to subscribers of combineLatest? i.e. I'm looking for an empty signal that just gets dropped, somehow.

i.e.:

let automaticUpdatesShouldBeEnabled: Observable<Bool>
let annotations: Observable<[PointAnnotation]>

combineLatest(automaticUpdatesShouldBeEnabled, annotations, {
    enabled, annotations in

    if enabled{ // cool, let the annotations through
        return annotations 
    }
    else{ // we want to stop here, and subscribers should receive nothing.
        // return ?? 
    }

})

from rxswift.

I guess one way would be to just make annotations an optional (Observable<[PointAnnotation]?>) and then just return nil - and then add a filter afterwards to filter these out.

But is there a better way?

from rxswift.

Hi @iandundas

I think what you need is a combo of combineLatest and flatMap. Something like:

let automaticUpdatesShouldBeEnabled: Observable<Bool>
let annotations: Observable<[PointAnnotation]>

combineLatest(automaticUpdatesShouldBeEnabled, annotations, { ($0, $1) })
    >- flatMap { enabled, annotations in
         if enabled{ // cool, let the annotations through
            return just(annotations) 
        }
        else{ // we want to stop here, and subscribers should receive nothing.
            return empty()
        }
     }

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That's perfect for what I need - thanks so much :)

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