Combine + Result.

result_sink.swift

/*
* 
* Use this when the publisher only publishes 1 value then stops.
*
*/

import Combine
import Foundation

extension Publisher {

    func sink(result handler: @escaping (Result<Output, Failure>) -> Void) -> AnyCancellable {
        return prefix(1).sink(receiveCompletion: { (completion) in
            if case let .failure(error) = completion {
                handler(.failure(error))
            }
        }, receiveValue: { (value) in
            handler(.success(value))
        })
    }
}

var tokens = Set<AnyCancellable>()

somePublisher.sink { (result) in 
 switch result {
   case .success(let payload):
     print(payload)
  case .failure(let error):
     print(error)
  }
}.store(in: &tokens)