ios - ReactiveCocoa combine SignalProducers into one

Question

I'm using ReactiveCocoa and I have several SignalProducers

let center = NSNotificationCenter.defaultCenter()
let signalProducer1 = center.rac_notification(name: notificationName1, object: nil)
let signalProducer2 = center.rac_notification(name: notificationName2, object: nil)
let signalProducer3 = center.rac_notification(name: notificationName3, object: nil)

I want to combine them into a single signal producer that produces a signal whenever one of them produces a signal.

At first the combineLatest function looked like a good solution

let combinedProducer = combineLatest(signalProducer1, signalProducer2, signalProducer3)

However, according to this article, the resulting producer only produces its first signal when all the three have produced a signal.

This interactive diagram shows exactly what I want, so I want to use the flatten function with the .Merge FlatteningStrategy. However, I'm having a hard time figuring out the syntax to achieve this.

Answer 1

更新：RAC 4.2.1 及更高版本

由于工作方式的变化，flatten我们需要帮助编译器更明确地了解类型：

let s1: SignalProducer<Int, NSError> = ...
let s2: SignalProducer<Int, NSError> = ...
let s3: SignalProducer<Int, NSError> = ...


let _: SignalProducer<Int, NSError> =
    SignalProducer<SignalProducer<Int, NSError>, NSError>(values: [s1, s2, s3])
        .flatten(.Merge)

这变得有点麻烦，所以你可能想要拆分它：

let producers: SignalProducer<SignalProducer<Int, NSError>, NSError> =
    SignalProducer(values: [s1, s2, s3])

let merged: SignalProducer<Int, NSError> = x.flatten(.Merge)

感谢@Harry 指出新版本问题的评论。

---

RAC 4.2 及以下

在 RAC 4 中，这将是

let merged = SignalProducer(values: [signalProducer1, signalProducer2, signalProducer3])
  .flatten(.Merge)

目前 Xcode 7.1.1 没有.flatten在自动完成窗口中提出建议，这可能会导致您（或只是我）认为它不存在，但如果您输入它，它会起作用。

Answer 2

您可以按如下方式实现：

let merged = SignalProducer(values: [ signalProducer1, signalProducer2, signalProducer3 ])
    |> flatten(.Merge)