话不多说，直接上代码

//
//  SFJTimer.h
//  定时器-GCD
//
//  Created by 宋法键 on 2019/8/14.
//  Copyright © 2019 WZSG. All rights reserved.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface SFJTimer : NSObject

+ (NSString *)executeTask:(void(^)(void))task start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeat:(BOOL)repeat async:(BOOL)async;

+ (NSString *)executeTask:(id)target selector:(SEL)selector start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeat:(BOOL)repeat async:(BOOL)async;

+ (void)cancelTask:(NSString *)taskSign;

@end

NS_ASSUME_NONNULL_END

//
//  SFJTimer.m
//  定时器-GCD
//
//  Created by 宋法键 on 2019/8/14.
//  Copyright © 2019 WZSG. All rights reserved.
//

#import "SFJTimer.h"

//多线程操作，需要加锁
static NSMutableDictionary *timers_;
static dispatch_semaphore_t semaphore_t_;

@implementation SFJTimer

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

+ (NSString *)executeTask:(void (^)(void))task start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeat:(BOOL)repeat async:(BOOL)async {
    
    if (!task || start < 0 || (interval <= 0 && repeat)) return nil;
    
    //获取队列
    //    dispatch_queue_t mainQueue = dispatch_get_main_queue();
    dispatch_queue_t queue = async ? dispatch_queue_create("serialQueue", DISPATCH_QUEUE_SERIAL) : dispatch_get_main_queue();
    
    //创建定时器
    dispatch_source_t timer_t = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    
    //设置时间
    dispatch_source_set_timer(timer_t, dispatch_time(DISPATCH_TIME_NOW, start * NSEC_PER_SEC), interval * NSEC_PER_SEC, 0);
    
    //加锁
    dispatch_semaphore_wait(semaphore_t_, DISPATCH_TIME_FOREVER);
    //定时器唯一标识
    NSString *taskSign = [NSString stringWithFormat:@"%lu", (unsigned long)timers_.count];
    timers_[taskSign] = timer_t;
    //解锁
    dispatch_semaphore_signal(semaphore_t_);
    
    //设置回调
    //两个方法同时写，只会有一个执行，而且是最后那个
//    dispatch_source_set_event_handler_f(timer_t, timerFunction);
    dispatch_source_set_event_handler(timer_t, ^{
        task();
        if (!repeat) {
            [self cancelTask:taskSign];
        }
    });
    
    //启动定时
    dispatch_resume(timer_t);
    
    return taskSign;
}

+ (NSString *)executeTask:(id)target selector:(SEL)aSelector start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeat:(BOOL)repeat async:(BOOL)async {
    
    if (!target || !aSelector) return nil;
    
    return [self executeTask:^{
        if ([target respondsToSelector:aSelector]) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
            [target performSelector:aSelector];
#pragma clang diagnostic pop
        }
    } start:start interval:interval repeat:repeat async:async];
}

+ (void)cancelTask:(NSString *)taskSign {
    if (!taskSign.length) return;
    
    //加锁
    dispatch_semaphore_wait(semaphore_t_, DISPATCH_TIME_FOREVER);
    dispatch_source_t timer_t = timers_[taskSign];
    if (!timer_t) return;
    
    dispatch_source_cancel(timers_[taskSign]);
    [timers_ removeObjectForKey:taskSign];
    //解锁
    dispatch_semaphore_signal(semaphore_t_);
}

@end

使用示例

//
//  ViewController.m
//  定时器-GCD
//
//  Created by 宋法键 on 2019/8/14.
//  Copyright © 2019 WZSG. All rights reserved.
//

#import "ViewController.h"
#import "SFJTimer.h"

@interface ViewController ()

@property (strong, nonatomic) dispatch_source_t timer_t;
@property (copy, nonatomic) NSString *taskSign1;
@property (copy, nonatomic) NSString *taskSign2;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    _taskSign1 = [SFJTimer executeTask:^{
        NSLog(@"-----aaaaa-----%@", [NSThread currentThread]);
    } start:2.0f interval:1.0f repeat:NO async:NO];
    
    _taskSign2 = [SFJTimer executeTask:self selector:@selector(doTask) start:2.0f interval:1.0f repeat:YES async:NO];
    
//    self.timer_t = timer_t;
}

- (void)doTask {
    NSLog(@"%s : %@", __func__, [NSThread currentThread]);
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [SFJTimer cancelTask:_taskSign1];
}

@end