Delay execution in iOS (Objective C & Swift 2 & Swift 3)

delay-swift3.swift

func delay(withTime: Double, callback: @escaping () -> Void) {
    let when = DispatchTime.now() + withTime
    DispatchQueue.main.asyncAfter(deadline: when) {
        callback()
    }
}

delay.m

double delayInSeconds = 0.5; // set the time
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
  // do something here        
});

delay.swift

let delayInSeconds = 4.5 * Double(NSEC_PER_SEC)
let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delayInSeconds))
dispatch_after(popTime, dispatch_get_main_queue()) {
  // do something here
}