Publishers and Subscribers in Combine.

Publishers-Subscribers.swift

import Foundation
import Combine

let publisherArr = [1.0, 2.0, 3.0, 4.0, 5.0, 6.0].publisher

// publisher is of type Publishers.Sequence<[Double], Never>

// the generic type here takes two arguments <Output, Failure>

// in this case the our publisherArr will "Never" fail.

// there are many publishers that can fail, take for example the URLSession.shared.dataTaskPublisher

// the Output is <Data, URLResponse>
// the Failuer is URLError

let dataTaskPublisher = URLSession.shared.dataTaskPublisher(for: URL(string: "alexpaul.dev")!)


publisherArr
  .sink(receiveCompletion: { (completion) in
    print(completion)
  }) { (cohort) in
    print("received value: \(cohort)")
}


// above we use .sink to subscribe to the values emitted from the publisherArr

// playground output:
/*
 received value: 1.0
 received value: 2.0
 received value: 3.0
 received value: 4.0
 received value: 5.0
 received value: 6.0
 finished
*/