iOS GCD定時器的使用

#import "ViewController.h"

@interface ViewController ()
{
    dispatch_source_t _timer;
    NSArray *arr;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.view.backgroundColor = [UIColor redColor];

    [self startGCDTimer];
}
-(void) startGCDTimer{
    NSTimeInterval period = 1.0; //設置時間間隔
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    dispatch_source_set_timer(_timer, dispatch_walltime(NULL, 0), period * NSEC_PER_SEC, 0); //每秒執行
    dispatch_source_set_event_handler(_timer, ^{
        //在這裏執行事件
        NSLog(@"每秒執行test");
    });

    dispatch_resume(_timer);
}


-(void) pauseTimer{
    if(_timer){
        dispatch_suspend(_timer);
    }
}
-(void) resumeTimer{
    if(_timer){
        dispatch_resume(_timer);
    }
}
-(void) stopTimer{
    if(_timer){
        dispatch_source_cancel(_timer);
        _timer = nil;
    }
}