Two countdown implementation methods for ios development

Method 1: Use nstimer

It mainly uses the scheduledtimerwithtimeinterval method of nstimer to execute the timefiremethod function every second. timefiremethod performs some countdown operations. After timer is completed, it is OK to give invalidate. The Code is as follows:

Secondscountdown = 60; // 60 seconds countdown countdowntimer = [nstimer scheduledtimerwithtimeinterval: 1 target: Self selector: @ selector (timefiremethod) userinfo: Nil repeats: Yes];-(void) timefiremethod {secondscountdown --; If (secondscountdown = 0) {[countdowntimer invalidate] ;}}

Method 2: Use GCD to implement

The Code is as follows:

_ Block int timeout = 300; // countdown time dispatch_queue_t queue = minute (hour, 0); dispatch_source_t _ timer = dispatch_source_create (hour, 0, 0, queue ); dispatch_source_set_timer (_ timer, dispatch_walltime (NULL, 0), 1.0 * NSEC_PER_SEC, 0); // second (_ timer, ^ {if (timeout <= 0) {// The countdown ends. Disable dispatch_source_cancel (_ time R); dispatch_release (_ timer); dispatch_async (dispatch_get_main_queue (), ^ {// the buttons on the settings page are displayed as needed ........ });} Else {int minutes = timeout/60; int seconds = timeout % 60; NSString * strTime = [NSString stringWithFormat: @ "% d %. get the verification code ", minutes, seconds]; dispatch_async (dispatch_get_main_queue (), ^ {// you can set the settings according to your needs ........ }); Timeout -- ;}}); dispatch_resume (_ timer );