ios - Dispatch and Delay between calls -
    i'm making clone old game simon (a.k.a. genius, in brazil), 1 coloured buttons player needs press following sequence of colors.   for testing, interface has 4 coloured buttons created array button outlets, easy access:   var buttonarray:[uibutton] = [self.greenbutton, self.yellowbutton, self.redbutton, self.bluebutton]   also, created array store sequence of colors   var colors:[int] = []   when game starts calls function adds random number 0 3 (index on buttonarray), , add number colors array after adding new color color sequence, app needs show sequence user, can repeat it   for that, calls playmoves function, uses loop run through colors array , change alpha button, simulating 'blink'   func playmoves(){      let delay = 0.5 * double(nsec_per_sec)     let time = dispatch_time(dispatch_time_now, int64(delay))          in self.colors{              self.buttonarray[i].alpha = 0.2              dispatch_after(time, dispatch_get_main_queue(), {                 self.buttona...