flattenMap new return type

[reactivecocoa]

flattenMap new return type

[erichoracek]

When I was updating the annotations, I checked this behavior. Returning a RACSequence from within the block provided to a -[RACSignal flattenMap:] will cause a crash. See https://github.com/ReactiveCocoa/ReactiveObjC/blob/master/ReactiveObjC/RACSignal.m#L108-L176 — specifically that the bindBlock()'s return value is cast to a RACSignal * and subscribeNext: is invoked on it, which is only available on RACSignal, not RACSequence.

It would appear that flattenMap: is not truly available on RACStream since bind: is not implemented on RACStream (subclasses must implement it). It seems best to think of RACStream as an protocol with some extensions that RACSignal and RACSequence both share, but they are generally not interoperable in practice.

[mdiep]

Maybe? I think this was done to make generics work well.

Are you actually returning a RACStream?

[beloso]

I am not returning a RACStream, I've noticed the change when migrating. All my flattenMaps were returning RACStream, but I always return a RACSignal. A simple find and replace fixed this for me.

I just wondered if the change was deliberate or a mistake perhaps.

[beloso]

I changed to ReactiveObjC specifically for the generics. So there is no need to change this back to RACStream on my end.

[beloso]

Thank you for your awesome explanation. It does indeed make sense to have change it to a RACSignal. I've never returned anything else actually.