Using combineLatest with UITextFields in RAC 3+

Question

I would like to simply "combine" the signals emitted by a number of textfields and fire a block of code. It seems there are a few ways this "should" work using methods like combineLatest() or the values: SignalProducer initializer. But I am not able to get anything to compile or function as expected.

RAC documentations uses the following example

combineLatest(numbersSignal, lettersSignal)
  |> observe(next: println, completed: { println("Completed") })

But I am not able to compile this kind of usage

I am able to do the following with redundant blocks...

locationTextfield.rac_textSignal().toSignalProducer()
  |> start(next: { txt in
    println(txt)
  })

aircraftTextfield.rac_textSignal().toSignalProducer()
  |>  start(next: { txt in
    println(txt)
  })

I also am not understanding why I need to use toSignalProducer() and start rather than just observing the rac_textsignal itself. This "compiles" but nothing seems to be sent on the signal unless a producer is created and started.

This question/answer ReactiveCocoa combine SignalProducers into one also works, but still seems like a work around, and doesn't explain why signal producers need to be created rather than observing the original rac_textSignal() s

Answer 1

Observing rac_textSignal without transformations is possible, we just need to clarify that rac_textSignal is RACSignal . RACSignal is the ReactiveCocoa 2.0 signal and is related to the Objective-C version. So you need to apply RAC2 operators to such signals, combineLatestWith: could help you to solve such task.

Transformations are necessary to apply Swift operators due to diff in the basic concept in RAC3. In RAC2 such core entity was RACSignal , against Signal and SignalProducer in the RAC3.