一: 分类封装

import UIKit

@objc public extension Timer{
    
    /// 分类方法
    static func scheduled(_ Interval: TimeInterval = 60, repeats: Bool = true, action: @escaping((Timer) -> Void)) -> Timer {
        return scheduledTimer(timeInterval: Interval, target: self, selector: #selector(handleInvoke(_:)), userInfo: action, repeats: repeats)
    }
    
    private static func handleInvoke(_ timer: Timer) {
        if let action = timer.userInfo as? ((Timer) -> Void) {
            action(timer)
        }
    }
    
    func activate() {
        //    继续：触发时间设置在现在/获取，这样定时器自动进入马上进入工作状态.
        self.fireDate = .distantPast
    }
    
    func pause() {
        //    暂停：触发时间设置在未来，既很久之后，这样定时器自动进入等待触发的状态.
        self.fireDate = .distantFuture
    }
    
    func destroy() {
        self.invalidate()
    }
        
    static func createGCDTimer(_ interval: TimeInterval = 60, repeats: Bool = true, action: @escaping(() -> Void)) -> DispatchSourceTimer {
        let codeTimer = DispatchSource.makeTimerSource(flags: .init(rawValue: 0), queue: DispatchQueue.global())
        codeTimer.schedule(deadline: .now(), repeating: .milliseconds(1000))
        codeTimer.setEventHandler {
            if repeats == false {
                codeTimer.cancel()
            }
            DispatchQueue.main.async(execute: action)
        }
        
        codeTimer.resume()
        return codeTimer;
    }
    
    static func destoryGCDTimer(_ timer: DispatchSourceTimer?) {
        timer?.cancel()
    }
}


public extension DispatchSourceTimer{
    
    static func create(_ interval: TimeInterval = 60, repeats: Bool = true, action: @escaping(() -> Void)) -> DispatchSourceTimer {
        let codeTimer = DispatchSource.makeTimerSource(flags: .init(rawValue: 0), queue: DispatchQueue.global())
        codeTimer.schedule(deadline: .now(), repeating: .milliseconds(1000))
        codeTimer.setEventHandler {
            if repeats == false {
                codeTimer.cancel()
            }
            DispatchQueue.main.async(execute: action)
        }
        
        codeTimer.resume()
        return codeTimer
    }
}

OC

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface NSTimer (Helper)
 
+ (NSTimer *)scheduledTimer:(NSTimeInterval)interval
                      block:(void(^)(NSTimer *timer))block
                    repeats:(BOOL)repeats;

///GCD定时器(秒)
+ (dispatch_source_t)createGCDTimer:(NSTimeInterval)interval
                            repeats:(BOOL)repeats
                              block:(void (^)(void))block;

+(void)destoryGCDTimer:(dispatch_source_t)timer;

///激活/启动
- (void)activate;
///暂停
- (void)pause;
//销毁
- (void)destroy;

@end

NS_ASSUME_NONNULL_END

#import "NSTimer+Helper.h"

@implementation NSTimer (Helper)

+ (NSTimer *)scheduledTimer:(NSTimeInterval)interval
                      block:(void(^)(NSTimer *timer))block
                    repeats:(BOOL)repeats{
    return [self scheduledTimerWithTimeInterval:interval
                                         target:self
                                       selector:@selector(handleInvoke:)
                                       userInfo:[block copy]
                                        repeats:repeats];
}

+ (void)handleInvoke:(NSTimer *)timer {
    void(^block)(NSTimer *timer) = timer.userInfo;
    if(block) {
        block(timer);
    }
}

+ (dispatch_source_t)createGCDTimer:(NSTimeInterval)interval
                            repeats:(BOOL)repeats
                              block:(void (^)(void))block{
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
    dispatch_source_set_timer(timer,dispatch_walltime(NULL, 0), interval * NSEC_PER_SEC, 0); //执行间隔
    dispatch_source_set_event_handler(timer, ^{
        if (!repeats) {
            dispatch_source_cancel(timer);
        }
        dispatch_async(dispatch_get_main_queue(), block);
        
    });
    dispatch_resume(timer); // 启动定时器
    return timer;
}
 
+(void)destoryGCDTimer:(dispatch_source_t)timer{
    if (timer) {
        dispatch_source_cancel(timer);
    }
}

- (void)activate{
    self.fireDate = NSDate.distantPast;
//    self.fireDate = NSDate.date;
}

- (void)pause{
    self.fireDate = NSDate.distantFuture;
}

- (void)destroy{
    [self invalidate];
//    self == nil;
}
@end

二.工具类封装

void dispatchTimer(id target, double timeInterval,void (^handler)(dispatch_source_t timer)){
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,0, 0, queue);
    dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), (uint64_t)(timeInterval *NSEC_PER_SEC), 0);
    // 设置回调
    __weak __typeof(target) weaktarget = target;
    dispatch_source_set_event_handler(timer, ^{
        if (!weaktarget)  {
            dispatch_source_cancel(timer);
            NSLog(@"dispatch_source_cancel!!!");
        } else {
            dispatch_async(dispatch_get_main_queue(), ^{
                if (handler) handler(timer);
            });
        }
    });
    // 启动定时器
    dispatch_resume(timer);
}

示例:
@property (nonatomic, strong) NSTimer *timer;

-(void)dealloc{
    [_timer destroy];
}

- (void)viewDidLoad {
    [super viewDidLoad];

    __block NSInteger i = 0;
    _timer = [NSTimer scheduledTimer:1 block:^(NSTimer *timer) {
        i++;
        DDLog(@"__%@",@(i));
    } repeats:YES];
    
    [NSTimer createGCDTimer:1 repeats:true block:^{
        i++;
        DDLog(@"%@",@(i));
    }];
    
    DDLog(@"___%@",@(i));
}

须知:
1. 调用 NSTimer 会对调用的对象 retain
2. NSTimer 必须加入 NSRunloop 中才能正确执行
3. NSTimer 并不是一个实时的系统(不准确)
4. NSRunLoopCommonModes 这是一个伪模式，是 run loop mode 的集合，此模式意味着在 Common Modes 中包含的所有模式下都可以处理。
在 Cocoa 应用程序中，默认情况下 Common Modes 包含 default modes, modal modes, event Tracking modes.
可使用 CFRunLoopAddCommonMode 方法想 Common Modes 中添加自定义 modes。