combine-flatMap-reduce-tryout.swift

import Combine
import Foundation
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

var publisher = PassthroughSubject<Int, Error>()

let cancellable = publisher
    .flatMap { Just($0).setFailureType(to: Error.self) }
    .handleEvents(
        receiveOutput: {(n:Int) in
            if n < 5 {
                publisher.send(n + 1)
            } else {
                publisher.send(completion: .finished)
            }
        }
    )
    .reduce([Int](), {allItems, n in
        print("Collecting items in reduce:", allItems.count)
        return allItems + [n]
    })
    .sink(
        receiveCompletion: {completion in
            switch completion {
            case .finished:
                print("Completed")
                break
            case .failure(let error):
                print(error.localizedDescription)
            }
        },
        receiveValue: { values in
            print("All values:", values)
        }
    )

publisher.send(1)