iOS GCD定时器

GCD定时器的优势是不受RunLoop的运行模式的影响，它的的间隔时间是纳秒为单位。

GCDTimer.h

#import <Foundation/Foundation.h>

typedef void (^TimerRunBlock)(NSUInteger currentTime);  //定时器计时回调
typedef void (^TimerStopBlock)();                       //定时器结束计时回调

@interface DPGCDTimer : NSObject

@property (nonatomic,assign)BOOL isTimerRuning;         //定时器是否正在运行
@property (nonatomic, copy) TimerStopBlock timerStopBlock;

/**
 *  定时器初始化(定时器默认开启)
 *
 *  @param timeDuration  时长
 *  @param timerRunBlock 定时器回调
 */
- (void)timerWithTimeDuration:(double)timeDuration withRunBlock:(TimerRunBlock)timerRunBlock;


/**
 *  定时器停止
 */
- (void)stopTimer;

/**
 *  定时器恢复
 */
- (void)resumeTimer;

/**
 *  定时器暂停
 */
- (void)suspendTimer;

@end

#import "DPGCDTimer.h"
#define WS(weakSelf)  __weak __typeof(&*self)weakSelf = self;

@interface DPGCDTimer ()
{
    dispatch_source_t __block timer;
}

@property (nonatomic,copy)TimerRunBlock timerRunBlock;

@end

@implementation DPGCDTimer

- (void)timerWithTimeDuration:(double)timeDuration withRunBlock:(TimerRunBlock)timerRunBlock
{
    if (!timer) {
        WS(weakSelf);
        //创建定时器
        _isTimerRuning = YES;
        NSUInteger __block time = timeDuration;
        
        self.timerRunBlock = timerRunBlock;
        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),1 * NSEC_PER_SEC, 0); //每秒执行
        dispatch_source_set_event_handler(timer, ^{
            if (time <= 0) {
                [self stopTimer];
            } else {
                if (weakSelf.timerRunBlock) {
                    weakSelf.timerRunBlock(time --);
                }
            }
        });
        dispatch_resume(timer);
    }
    
}

//停止
- (void)stopTimer
{
    if(timer){
        if (_isTimerRuning) {
            dispatch_source_cancel(timer);
            timer = nil;
            _isTimerRuning = NO;
            if (self.timerStopBlock) {
                self.timerStopBlock();
            }
        }
        
    }
}

//恢复
- (void)resumeTimer
{
    if(timer){
        if (!_isTimerRuning) {
            dispatch_resume(timer);
            _isTimerRuning = YES;
        }
        
    }
}

//暂停
- (void)suspendTimer
{
    if(timer){
        if (_isTimerRuning) {
            dispatch_suspend(timer);
            _isTimerRuning = NO;
        }
    }
}


@end

PS:
GCD 中刷新UI导致线程崩溃问题工具 - PSPDFUIKitMainThreadGuard
工具使用方法就是把这个.m文件拖入工程，如果有问题就会PSPDFAssert断点处停住。在左侧线程分析中点击查看出现错误的地方。