Runloop应用：线程保活

应用场景：

• 经常在子线程中做事情。

实现：

• 实现逻辑：

  1. 创建一个子线程；
  2. 在子线程里添加一个runloop。

• 封装实现：

typedef void (^PermenantThreadTask)(void);

@interface PermenantThread : NSObject

/**
 在当前子线程执行一个任务
 */
- (void)executeTask:(PermenantThreadTask)task;

/**
 结束线程
 */
- (void)stop;

@end

@interface PermenantThread()
@property (strong, nonatomic) NSThread *innerThread;
@property (assign, nonatomic, getter=isStopped) BOOL stopped;
@end

@implementation PermenantThread
- (instancetype)init {
    if (self = [super init]) {
        self.stopped = NO;
        
        __weak typeof(self) weakSelf = self;
        
        self.innerThread = [[NSThread alloc] initWithBlock:^{
            [[NSRunLoop currentRunLoop] addPort:[[NSPort alloc] init] forMode:NSDefaultRunLoopMode];
            
            while (weakSelf && !weakSelf.isStopped) {
                [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
            }
        }];
        
        [self.innerThread start];
    }
    return self;
}

- (void)executeTask:(PermenantThreadTask)task {
    if (!self.innerThread || !task) return;
    
    [self performSelector:@selector(__executeTask:) onThread:self.innerThread withObject:task waitUntilDone:NO];
}

- (void)stop {
    if (!self.innerThread) return;
    
    [self performSelector:@selector(__stop) onThread:self.innerThread withObject:nil waitUntilDone:YES];
}

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

#pragma mark - private methods
- (void)__stop {
    self.stopped = YES;
    CFRunLoopStop(CFRunLoopGetCurrent());
    self.innerThread = nil;
}

- (void)__executeTask:(PermenantThreadTask)task {
    task();
}

@end