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April 10, 2021 21:19
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Composed implementation of `Publisher.withLatestFrom`’s that handled finished events.
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| extension Publisher { | |
| func withLatestFrom<Other: Publisher>( | |
| _ other: Other | |
| ) -> AnyPublisher<Other.Output, Other.Failure> | |
| where Failure == Other.Failure { | |
| let upstream = share() | |
| return other | |
| .map { second in upstream.map { _ in second } } | |
| .switchToLatest() | |
| .zip(upstream) // `zip`ping and discarding `\.1` allows for | |
| // upstream completions to be projected down immediately. | |
| .map(\.0) | |
| .eraseToAnyPublisher() | |
| } | |
| } | |
| let first = PassthroughSubject<Int, Never>() | |
| let second = PassthroughSubject<String, Never>() | |
| var cancellables = Set<AnyCancellable>() | |
| first | |
| .withLatestFrom(second) | |
| .sink(receiveCompletion: { print($0) }, receiveValue: { print($0) }) | |
| .store(in: &cancellables) | |
| first.send(completion: .finished) | |
| // Outputs: | |
| // | |
| // ``` | |
| // finished | |
| // ``` |
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