swift + CombineフレームワークのFuture + DispatchQueueを組み合わせる

future_and_dispatch.swift

import Combine
import SwiftUI

func run1() -> Future<String, Never>{
    return Future{ promise in
        promise(.success("OK1: \(Thread.isMainThread)"))
    }
}

func run2() -> Future<String, Never>{
    return Future{ promise in
        DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
            print("OK2: \(Thread.isMainThread)")
            promise(.success("OK3: \(Thread.isMainThread)"))
        }
    }
}

DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
    print("OK4: \(Thread.isMainThread)")
}

run1().sink { print("data: \($0)")}
run2().sink { print("data: \($0)")}

gistfile1.txt

data: OK1: true
OK2: true
OK4: true  // <- OK2が出てほしい