CODEWITHSUNDEEP
iosobjective-creactive-cocoa
mag_zbc
mag_zbc

Reputation: 6982

ReactiveCocoa - flattenMap block never called

I have a problem using flattenMap method of RACSignal - the block never gets called. If I subscribeNext to the same signal, it works just fine, the problem is only with flattenMap.

Here's what works fine 

[[self.aSignal combineLatestWith:self.otherSignal] subscribeNext:^(RACTuple *tuple) {
    // gets called just fine
}];

And here's what doesn't work: 

self.yetAnotherSignal = [[self.aSignal combineLatestWith:self.otherSignal] flattenMap:^RACStream *(RACTuple *tuple) {
    // never gets called
    return returnSignal;
}];

Am I missing something? Or do I misunderstand how flattenMap works?

Upvotes: 0

Views: 50

Answers (1)

MeXx
MeXx

Reputation: 3357

It seems like you're missing just one little bit: (at least in your snippet) no one is subscribing to your new signal!

You're constructing a new signal (self.yetAnotherSignal) from self.aSignal and self.otherSignal via combineLatest and flattenMap.

But that new signal, as well as any operators in the chain, do not actually do any work until it is subscribed in some form, the simplest form being via subscribeNext just as you did in your first snippet.

That is not just the case with flattenMap, its the same with any operation, e.g. combineLatestWith in your first example would not do anything if you would not subscribe to it. The same goes for map, filter, ... you name it.

Upvotes: 1

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