GCXTimer.h

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface GCXTimer : NSObject

/**
 *  task 执行的任务
 *  start   开始间隔时间
 *  interval    timer间隔时间
 *  repeats 是否重复
 *  async   是否异步
 */
+ (NSString *)execTask:(void(^)(void))task
                 start:(NSTimeInterval)start
              interval:(NSTimeInterval)interval
               repeats:(BOOL)repeats
                 async:(BOOL)async;

/**
 *  target  添加定时器的目标
 *  selector   回调方法
 *  interval    timer间隔时间
 *  repeats 是否重复
 *  async   是否异步
 */
+ (NSString *)execTarget:(id)target
                selector:(SEL)selector
                   start:(NSTimeInterval)start
                interval:(NSTimeInterval)interval
                 repeats:(BOOL)repeats
                   async:(BOOL)async;

/**
 * 取消定时器
 * task 定时器的唯一标识
 */
+ (void)cancelTimerTask:(NSString *)task;

@end

NS_ASSUME_NONNULL_END

GCXTimer.m

#import "GCXTimer.h"

@interface GCXTimer()

@end

@implementation GCXTimer

static NSMutableDictionary *timers_;
static dispatch_semaphore_t semaphore_;
+ (void)initialize {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        timers_ = [NSMutableDictionary dictionary];
        semaphore_ = dispatch_semaphore_create(1);
    });
    
}

/**
 *  task        执行的任务
 *  start       开始间隔时间
 *  interval    timer间隔时间
 *  repeats     是否重复
 *  async       是否异步
 *  返回值为定时器的唯一标识
 */
+ (NSString *)execTask:(void (^)(void))task start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeats:(BOOL)repeats async:(BOOL)async {
    
    if (!task || start < 0 || (interval <= 0 && repeats)) return nil;
    
    //队列
    dispatch_queue_t queue = async ? dispatch_get_global_queue(0, 0) : dispatch_get_main_queue();

    //创建定时器
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    //设定时间
    dispatch_source_set_timer(timer, dispatch_time(DISPATCH_TIME_NOW, start*NSEC_PER_SEC), interval*NSEC_PER_SEC, 0);
    
    //加锁
    dispatch_semaphore_wait(semaphore_, DISPATCH_TIME_FOREVER);
    
    //定时器的唯一标识
    NSString *name = [NSString stringWithFormat:@"%zd",timers_.count];
    
    timers_[name] = timer;
    
    //发送信号（解锁）
    dispatch_semaphore_signal(semaphore_);

    //设置回调
    dispatch_source_set_event_handler(timer, ^{
        task();
        if (!repeats) {//不重复的任务
            [self cancelTimerTask:name];
//            dispatch_source_cancel(timer);
        }
    });
    //启动定时器
    dispatch_resume(timer);
        
    return name;
}

/**
 *  target  添加定时器的目标
 *  selector   回调方法
 *  interval    timer间隔时间
 *  repeats 是否重复
 *  async   是否异步
 */
+ (NSString *)execTarget:(id)target selector:(SEL)selector start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeats:(BOOL)repeats async:(BOOL)async {
    if (!target || !selector)   return nil;
    
    return [self execTask:^{
        if ([target respondsToSelector:selector]) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
// 要消息的代码块
            [target performSelector:selector];
// 被夹在这中间的代码针对于此警告都会无视并且不显示出来
#pragma clang diagnostic pop
        }
    } start:start interval:interval repeats:repeats async:async];
}

/**
 * 取消定时器
 * task 定时器的唯一标识
 */
+ (void)cancelTimerTask:(NSString *)task {
    
    if (task.length == 0) {
        return;
    }
    //加锁
    dispatch_semaphore_wait(semaphore_, DISPATCH_TIME_FOREVER);
    dispatch_source_t timer = timers_[task];
    if (timer) {
        dispatch_source_cancel(timers_[task]);
        [timers_ removeObjectForKey:task];
    }
    
    //发送信号（解锁）
    dispatch_semaphore_signal(semaphore_);

}

@end

使用示例：

@property (nonatomic, copy) NSString *timerId;/**< 定时器标识 */

//创建定时器
self.timerId = [GCXTimer execTask:^{
        //自己的代码块
} start:0.0 interval:1.0f repeats:YES async:NO];

//取消定时器
[GCXTimer cancelTimerTask:self.timerId];