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Cold publisher double `Sink` with distinct subscribers.
import PlaygroundSupport /// (1) We’ll need this import to allow for indefinite execution.
PlaygroundPage.current.needsIndefiniteExecution = true
enum SomeError: Error {
case anError
}
let requestURL = URL(string: "https://picsum.photos/v2/list")!
struct Photo: Decodable {
var id: String
}
var attemptCount = 1
let coldPublisher: AnyPublisher<[Photo], Error> = URLSession.shared
.dataTaskPublisher(for: requestURL)
.map(\.data)
.decode(type: [Photo].self, decoder: JSONDecoder())
.tryMap {
defer { attemptCount += 1 }
if attemptCount.isMultiple(of: 2) {
return $0
} else {
throw SomeError.anError
}
}
.eraseToAnyPublisher()
let sink1 = Subscribers.Sink<[Photo], Error>(
receiveCompletion: { print("1: \($0)") },
receiveValue: { print("1: \($0.map(\.id))") }
)
let sink2 = Subscribers.Sink<[Photo], Error>(
receiveCompletion: { print("2: \($0)") },
receiveValue: { print("2: \($0.map(\.id))") }
)
coldPublisher
.subscribe(sink1)
DispatchQueue.main.asyncAfter(deadline: .now() + 2) { /// (2) Tacking on some delay to make things more clear.
coldPublisher
.subscribe(sink2)
}
/// (3) Output:
/// ```none
/// 1: failure(__lldb_expr_55.SomeError.anError)
/// 2: ["0", "1", "10", "100", "1000", "1001", "1002", "1003", "1004", "1005", "1006", "1008", "1009", "101", "1010", "1011", "1012", "1013", "1014", "1015", "1016", "1018", "1019", "102", "1020", "1021", "1022", "1023", "1024", "1025"]
/// 2: finished
/// ```
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