RACSubject migration to ReactiveCocoa 5 (Swift 3)

Question

I have to migrate an application from ReactiveCocoa 4 to ReactiveCocoa 5 (due to Swift 3 migration)

The old implementation uses some RACSubject instances for triggering (performOperationSubject.sendNext) an operation and for handling (didOperationSubject.subscribeNext) the result

internal class MyClass {

internal var performOperationSubject: RACSubject = RACSubject()
internal var didOperationSubject: RACSubject = RACSubject()

internal overide init() {
  super.init()
  self.performOperationSubject.subscribeNext { [weak self](_) in
    guard let strongSelf = self else { return }
    strongSelf.didOperationSubject.sendNext(result)

}

}

and when the MyClass instance is used

myClassInstance.didOperationSubject.subscribeNext { ... }

myClassInstance.performOperationSubject.sendNext(value)

Unfortunately the RACSubject is no more present in ReactiveCocoa 5 (ReactiveSwift)

How can I replace the RACSubject in this context?

score 3 · Accepted Answer · edited Jun 29 '17 at 12:18

You would use pipe which gives you an input observer and an output signal instead of using a RACSubject for both input and output. The example from the ReactiveSwift docs looks like this:

let (signal, observer) = Signal<String, NoError>.pipe()

signal
    .map { string in string.uppercased() }
    .observeValues { value in print(value) }

observer.send(value: "a")     // Prints A
observer.send(value: "b")     // Prints B
observer.send(value: "c")     // Prints C

Using Signal.pipe instead of RACSubject:

Since the Signal type, like RACSubject, is always “hot”, there is a special class method for creating a controllable signal. The Signal.pipe method can replace the use of subjects, and expresses intent better by separating the observing API from the sending API.

To use a pipe, set up observers on the signal as desired, then send values to the sink:

let (signal, observer) = Signal<String, NoError>.pipe()

signal.observeValue(value in
    // use value
})

observer.send(value: "the value")

I have found a more specific reference about this issue on the ReactiveCocoa change log https://github.com/ReactiveCocoa/ReactiveCocoa/blob/master/CHANGELOG.md#using-signalpipe-instead-of-racsubject — cristallo, Jun 26 '17 at 08:55

RACSubject migration to ReactiveCocoa 5 (Swift 3)

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