CombineStreamFail_HowToOverCome

CombineStreamFail_HowToOverCome.swift

// Example of One-Shot piblisher with Stream Failure. 
// As we find the value 0 in the stream, we throw an error. This error is eventually catched and replaced with Just(-1) publisher.
// But after a failed value will activates the catch operator and the pipeline will cease to react further.
struct SimpleError: Error {}
let numbers = [5, 4, 3, 2, 1, 0, 9, 8, 7, 6]

let cancellable = numbers.publisher
    .tryMap({ val in
        guard val != 0 else {throw SimpleError()}
        return val

    })
    .catch({ (error) in
        Just(-1)
    })
    .sink { print("\($0)") }


// To continue with the stream to respond and handle error on emmited value we'll be using combination of flatMap with catch.

// Uncomment this and comment out above pipeline. We'll see the even after getting 0 value which is replaced with -1, our pipeline continue to respond.
/*
let cancellable = numbers.publisher
    .flatMap({ val in
        Just(val).tryMap({
            guard $0 != 0 else {throw SimpleError()}
            return $0
        })
        .catch({ (error) in
            Just(-1)
        })
    })
    .sink { print("\($0)") }
*/