In the second beta of the Swift framework Combine there was no easy way to split a publisher output of type Sequence into separate values for every element in the sequence. This extension to Publisher adds an operator to do this.

Publisher+sequence.swift

import Combine

extension Publisher where Output: Sequence {
    func sequence() -> Publishers.FlatMap<Publishers.Sequence<Self.Output, Self.Failure>, Self> {
        self.flatMap { Publishers.Sequence(sequence: $0) }
    }
}

let publisher = PassthroughSubject<Array<Int>, Never>()
publisher
    .sink {
        print($0)
    }
publisher.send([1, 2, 3, 4, 5])
publisher.send([1, 2, 3, 4, 5])

// Prints: 
// [1, 2, 3, 4, 5]
// [1, 2, 3, 4, 5]


let publisher2 = PassthroughSubject<Array<Int>, Never>()
publisher2
    .sequence()
    .sink {
        print($0)
    }
publisher2.send([1, 2, 3, 4, 5])
publisher2.send([1, 2, 3, 4, 5])

// Prints: 
// 1
// 2
// 3
// 4
// 5
// 1
// 2
// 3
// 4
// 5