Combining operator: switchToLatest()

SwitchToLatest.swift

let intPublisher1 = PassthroughSubject<Int, Never>()
let intPublisher2 = PassthroughSubject<Int, Never>()

let publishers = PassthroughSubject<PassthroughSubject<Int, Never>, Never>()

publishers.switchToLatest().sink { print($0) }

publishers.send(intPublisher1)

intPublisher1.send(-3)
intPublisher1.send(-5)
intPublisher2.send(0)   // Zero will not be published as publisher listening for latest publisher.

publishers.send(intPublisher2)

intPublisher2.send(100)
intPublisher2.send(200)

// Output:
//    -3
//    -5
//    100
//    200