简易封装的 GCD 定时器

GCD定时器相比NSTimer可以忽略 Runloop带来的问题，同时也更加精确。

封装如下

#import <Foundation/Foundation.h>

@interface GCDTimer : NSObject

//新建 timer
+ (dispatch_source_t )timerWithTimeInterval:(NSTimeInterval)timeInterval
                        delay:(NSTimeInterval)delay
                        block:(void(^)(id timer))block;

//开启
+ (void)startWithTimer:(dispatch_source_t)timer;

//取消
+ (void)cancelWithTimer:(dispatch_source_t)timer;

//暂停
+ (void)pauseWithTimer:(dispatch_source_t)timer;
@end

#import "GCDTimer.h"

@interface GCDTimer()
//@property (nonatomic, strong) dispatch_source_t timer;

@end

@implementation GCDTimer

+ (dispatch_source_t )timerWithTimeInterval:(NSTimeInterval)timeInterval
                        delay:(NSTimeInterval)delay
                        block:(void (^)(id))block{
    dispatch_queue_t queue = dispatch_get_main_queue();
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    dispatch_time_t start = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * NSEC_PER_SEC));
    uint64_t interval = (uint64_t)(timeInterval * NSEC_PER_SEC);
    dispatch_source_set_timer(timer, start, interval, 0);
    dispatch_source_set_event_handler(timer, ^{
        if(block){
            block(timer);
        }
    });
    return timer;
}

+ (void)startWithTimer:(dispatch_source_t)timer{
    if(timer){
        dispatch_resume(timer);
    }
}

+ (void)pauseWithTimer:(dispatch_source_t)timer{
    if(timer){
        dispatch_suspend(timer);
    }
}

+ (void)cancelWithTimer:(dispatch_source_t)timer{
    if(timer){
        dispatch_cancel(timer);
    }
}

@end

使用

- (void)viewDidLoad {
    [super viewDidLoad];
    __block NSInteger i = 0;
    dispatch_source_t timer = [GCDTimer timerWithTimeInterval:1
                              delay:0
                              block:^(id timer) {
                                  i+=1;
                                  NSLog(@"** %ld **",i);
                                  if(i==20){
                                      [GCDTimer cancelWithTimer:timer];
                                  }
                              }];
    [GCDTimer startWithTimer:timer];
}

如有不正确的地方，还请各位多多指教。