wait for condition to be true

WaitUntil.swift

import Foundation

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

func waitUntil(timeout: Double, @autoclosure _ checkSuccess:  ()->Bool) -> Bool {
	let startDate = NSDate()
	var success = false
	while !success && abs(startDate.timeIntervalSinceNow) < timeout {
		NSRunLoop.currentRunLoop().runUntilDate(NSDate(timeIntervalSinceNow: 0.01))
		success = checkSuccess()
	}
	return success
}

Add @discardableResult if you want those missing assignment warnings to go away