Swift Playground for Publishers using Merge, CombineLatest & Zip

gistfile1.txt

import Foundation
import Combine

var count = 0

enum Marker: CustomDebugStringConvertible {
  case A(Int)
  case B(Int)
  
  var debugDescription: String {
    switch self {
    case .A(let time):
      return "A\(time)\(time == count ? "*" : "")"
    case .B(let time):
      return "B\(time)\(time == count ? "*" : "")"
    }
  }
}

Timer.publish(every: 1, on: .main, in: .default)
  .autoconnect()
  .sink { _ in count += 1 }

let publisherA = Timer.publish(every: 2, on: .main, in: .default)
  .autoconnect()
  .map { _ in Marker.A(count) }

let publisherB = Timer.publish(every: 3, on: .main, in: .default)
  .autoconnect()
  .map { _ in Marker.B(count) }

Publishers.Merge(publisherA, publisherB)
.sink { print("Time \(count): Merge \($0)") }

Publishers.CombineLatest(publisherA, publisherB)
  .sink { print("Time \(count): CombineLatest \($0), \($1)") }

Publishers.Zip(publisherA, publisherB)
  .sink { print("Time \(count): Zip \($0), \($1)") }

RunLoop.main.run()

/* Using Merge

Time 2: Merge A2*
Time 3: Merge B3*
Time 4: Merge A4*
Time 6: Merge A6*
Time 6: Merge B6*
Time 8: Merge A8*
Time 9: Merge B9*
Time 10: Merge A10*
Time 12: Merge A12*
Time 12: Merge B12*

Publishes any time any Publisher publishes.

*/

/* Using CombineLatest 

Time 3: CombineLatest A2, B3*
Time 4: CombineLatest A4*, B3
Time 6: CombineLatest A6*, B3
Time 6: CombineLatest A6*, B6*
Time 8: CombineLatest A8*, B6
Time 9: CombineLatest A8, B9*
Time 10: CombineLatest A10*, B9
Time 12: CombineLatest A12*, B9
Time 12: CombineLatest A12*, B12*
Time 14: CombineLatest A14*, B12

Publishes tuple of most recent Output any time any Publisher publishes, starting after all Publishers have published something.

*/

/* Using Zip

Time 3: Zip A2, B3*
Time 6: Zip A4, B6*
Time 9: Zip A6, B9*
Time 12: Zip A8, B12*
Time 15: Zip A10, B15*
Time 18: Zip A12, B18*
Time 21: Zip A14, B21*
Time 24: Zip A16, B24*

Publishes tuple of most recent Output when all Publishers have published something new.

*/