Runloop

    // 获取 runloop对象
    // foundation
    NSRunLoop *mloop = [NSRunLoop mainRunLoop];
    NSRunLoop *loop = [NSRunLoop currentRunLoop];
    
    // core foundation
    CFRunLoopRef cloop = CFRunLoopGetCurrent();
    CFRunLoopRef cmloop = CFRunLoopGetMain();

// observer状态回调
void runLoopObserverCallBack(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info)
{
    // 打印当前的mode
    CFRunLoopMode mode = CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent());
    NSLog(@"----mode: %@", mode);
    CFRelease(mode);
    
//    NSLog(@"runLoopObserverCallBack->%@, %@", observer, info);
    switch (activity) {
        case kCFRunLoopEntry:
            NSLog(@"kCFRunLoopEntry");
            break;
        case kCFRunLoopBeforeTimers:
            NSLog(@"kCFRunLoopBeforeTimers");
        break;
        case kCFRunLoopBeforeSources:
            NSLog(@"kCFRunLoopBeforeSources");
        break;
        case kCFRunLoopBeforeWaiting:
            NSLog(@"kCFRunLoopBeforeWaiting");
        break;
        case kCFRunLoopAfterWaiting:
            NSLog(@"kCFRunLoopAfterWaiting");
        break;
        case kCFRunLoopExit:
            NSLog(@"kCFRunLoopExit");
        break;
        case kCFRunLoopAllActivities:
            NSLog(@"kCFRunLoopAllActivities");
        break;
    }
}
{
// 创建观察者
    // 使用函数来响应事件
    CFRunLoopObserverRef observer
    = CFRunLoopObserverCreate(kCFAllocatorDefault,
                              /*CFAllocatorRef allocator*/
                               kCFRunLoopEntry |
                              kCFRunLoopBeforeTimers |
                              kCFRunLoopBeforeSources |
                              kCFRunLoopBeforeWaiting |
                              kCFRunLoopAfterWaiting |
                              kCFRunLoopExit |
                              kCFRunLoopAllActivities,
                              /*CFOptionFlags activities*/
                              true,
                              /*Boolean repeats*/
                              0,
                              /*CFIndex order*/
                              &runLoopObserverCallBack,
                              /*CFRunLoopObserverCallBack callout*/
                              nil
                              /*CFRunLoopObserverContext *context*/
                              );
                                                            
    
    // 使用 block 来响应事件
    CFRunLoopObserverRef observer1
    = CFRunLoopObserverCreateWithHandler(kCFAllocatorDefault,
                                         kCFRunLoopEntry |
                                         kCFRunLoopBeforeTimers |
                                         kCFRunLoopBeforeSources |
                                         kCFRunLoopBeforeWaiting |
                                         kCFRunLoopAfterWaiting |
                                         kCFRunLoopExit |
                                         kCFRunLoopAllActivities,
                                         true,
                                         0,
                                         ^(CFRunLoopObserverRef observer,
                                           CFRunLoopActivity activity) {
                                            
                                            // 监听mode切换
                                            switch (activity) {
                                                case kCFRunLoopEntry:
                                                {
                                                    CFRunLoopMode mode = CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent());
                                                                                        
                                                    NSLog(@"----mode: %@", mode);
                                                    CFRelease(mode);
                                                    NSLog(@"kCFRunLoopEntry");
                                                }
                                                    break;
                                                case kCFRunLoopExit:
                                                {
                                                    CFRunLoopMode mode = CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent());
                                                                                        
                                                    NSLog(@"----mode: %@", mode);
                                                    CFRelease(mode);
                                                    NSLog(@"kCFRunLoopExit");
                                                }
                                                break;
                                                case kCFRunLoopAllActivities:
                                                    NSLog(@"kCFRunLoopAllActivities");
                                                break;
                                                default:
                                                    break;
                                            }
        
                                        });
    
    // 添加runloop观察者
    CFRunLoopAddObserver(CFRunLoopGetMain(), observer1, kCFRunLoopCommonModes);
    
    CFRelease(observer);
    CFRelease(observer1);
}

/// Creates and returns a new NSTimer object initialized with the
// specified block object and schedules it on the current run loop 
// in the default mode.
[NSTimer scheduledTimerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
        static int a = 0;
        CFRunLoopMode mode =  CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent());
        NSLog(@"%@:%d", mode, a++);
        CFRelease(mode);
}];

NSTimer *timer = [NSTimer timerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
            static int a = 0;
            CFRunLoopMode mode =  CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent());
            NSLog(@"%@:%d", mode, a++);
            CFRelease(mode);
    }];
    
//NSRunLoopCommonModes = UITrackingRunLoopMode | NSDefaultRunLoopMode
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(test) object:nil];
[thread start];

self.stopRunloop = false;
__weak typeof(self) weakSelf = self;
// 如果不开启一个运行中的runloop，线程执行完一个事件时候就关闭
AYThread *thread = [[AYThread alloc] initWithBlock:^{
    NSLog(@"%s, %@", __func__, [NSThread currentThread]);
    
    // 线程保活，添加Port 或者 Timer，不然执行完这个函数线程就释放了.即使被强引用
    [[NSRunLoop currentRunLoop] addPort:[[NSPort alloc] init] forMode:NSDefaultRunLoopMode];
    
    //        static int count = 0;
    //        NSTimer *timer = [NSTimer timerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
    //            NSLog(@"%d", count++);
    //        }];
    //        [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
    
    
    // 查看官方注释, 使用这种方法只要有source, runloop永远不会结束
    // [[NSRunLoop currentRunLoop] run];
    
    
    // 重复启动runloop让线程保活
    while (weakSelf && !weakSelf.isStopRunloop)
    {
        // 处理完一个事件之后，这个runloop就结束了，
        // 会进入while循环再次开启runloop等待事件
        NSLog(@"runloop run");
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
    }
}];
    
[thread start];
self.thread = thread;

// waitUntilDone:NO 直接继续执行下面的代码
// waitUntilDone:YES 等Selector执行完成后再执行后面的代码
// 使用同一个线程，处理串行任务
[self performSelector:@selector(test) onThread:self.thread withObject:nil waitUntilDone:NO];

- (void)dealloc
{
    [self removeThread];
    NSLog(@"%s", __func__);
}

- (void)stopRunloop
{   
    // 进入子线程中，停止当前runloop
    CFRunLoopStop(CFRunLoopGetCurrent());
}

- (void)removeThread
{
    NSLog(@"%s", __func__);
    if (self.thread != nil)
    {
        self.stopRunloop = true;
        [self performSelector:@selector(stopRunloop) onThread:self.thread withObject:nil waitUntilDone:YES];
        self.thread = nil;
    }
}