CODEWITHSUNDEEP
iosswiftxcodecombine
user1261347
user1261347

Reputation: 325

Deriving Publisher from different publishers in Combine

I have a property with a fixed type

var statusPublisher: Published<Status>.Publisher

and some other statuses like substatus1, substatus2

and I want it to combine values of other statuses like

var statusPublisher: Published<Status>.Publisher {
    $substatus1.combineLatest($substatus2).map { s1, s2 -> Status in ... }
}

but it says Cannot convert return expression of type 'Publishers.CombineLatest<Published<Substatus1>.Publisher, Published<Substatus2>.Publisher>' to return type 'Published<Status>.Publisher'

I managed to workaround it with one extra

var connectionStatusSubject = PassthroughSubject<Status, Never>()

that I put into

var connectionStatusPublisher: AnyPublisher<Status, Never> {
    connectionStatusSubject.eraseToAnyPublisher()
}

with new AnyPublisher here, but it seems not so neat.

Is there any way to make it the right way?

Upvotes: 1

Views: 395

Answers (1)

New Dev
New Dev

Reputation: 49590

Published<T>.Publisher is just a specific type of a publisher, created by @Published property wrapper. There's no reason at all to use that as the type of the computed property.

Type-erase to AnyPublisher - like you did with PassthroughSubject - except you don't need a PassthroughSubject:

var statusPublisher: AnyPublisher<Status, Never> {
    $substatus1
       .combineLatest($substatus2)
       .map { s1, s2 -> Status in ... }
       .eraseToAnyPublisher()
}

Upvotes: 2

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