Publishers.Zip4
A publisher created by applying the zip function to four upstream publishers.
Declaration
struct Zip4<A, B, C, D> where A : Publisher, B : Publisher, C : Publisher, D : Publisher, A.Failure == B.Failure, B.Failure == C.Failure, C.Failure == D.FailureOverview
Use a Publishers.Zip4 to combine the latest elements from four publishers and emit a tuple to the downstream. The returned publisher waits until all four publishers have emitted an event, then delivers the oldest unconsumed event from each publisher as a tuple to the subscriber.
If any upstream publisher finishes successfully or fails with an error, so too does the zipped publisher.