waitUntil.swift

func waitUntil(_ done: @escaping (@escaping () -> Void) -> Void) {
    var completed: UInt32 = 0
    DispatchQueue.main.async {
        done { OSAtomicOr32Barrier(1, &completed) }
    }

    while completed == 0 {
        RunLoop.current.run(until: Date(timeIntervalSinceNow: 0.01))
    }
}