wait for condition to be true

WaitUntil.swift

import Foundation

func waitUntil(_ checkSuccess: @autoclosure ()->Bool) {
    return waitUntil(1.0, checkSuccess)
}

func waitUntil(_ timeout: Double, _ checkSuccess: @autoclosure ()->Bool) {
    let startDate = NSDate()
    var success = false
    while !success && abs(startDate.timeIntervalSinceNow) < timeout {
        RunLoop.current.run(until: Date(timeIntervalSinceNow: 0.01))
        success = checkSuccess()
    }
}