Use Grand Central Dispatch:
@property (strong, nonatomic) dispatch_source_t timer;
- (void)startTimer
{
if (!self.timer) {
self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());
}
if (self.timer) {
dispatch_source_set_timer(self.timer, dispatch_walltime(NULL, 0), 60ull*NSEC_PER_SEC, 10ull*NSEC_PER_SEC);
dispatch_source_set_event_handler(_timer, ^(void) {
[self tick];
});
dispatch_resume(_timer);
}
}
- (void)tick
{
// Do your REST query here
}
This will invoke your tick
method every 60 seconds.
To suspend and resume your timer, use dispatch_suspend and dispatch_resume:
dispatch_suspend(self.timer);
dispatch_resume(self.timer);
You can invoke dispatch_source_set_timer
at any time later to schedule ticks sooner or delay them until later:
// Fire sooner than 60 seconds, but resume 60s fires after that
unsigned long long delaySeconds = arc4random() % 60;
dispatch_source_set_timer(self.timer, dispatch_walltime(NULL, delaySeconds * NSEC_PER_SEC), 60ull*NSEC_PER_SEC, 10ull*NSEC_PER_SEC);
See the Apple Concurrency Programming Guide for full docs on this.