线程锁

探讨iOS开发中各种锁
使用NSCondition实现多线程同步

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    NSLog(@"--");
    
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        sleep(2);
        [_cityCondition lock];
        [_cityCondition signal];
        [_cityCondition unlock];
    });
    
    NSLog(@"%d", [self ff]);
    
    NSLog(@"====");
    
    return YES;
}

- (BOOL)ff {
    if (!_cityCondition) {
        _cityCondition = [[NSCondition alloc] init];
    }
    
    [_cityCondition lock];
    [_cityCondition wait];
    [_cityCondition unlock];
    
    return 1;
}

NSCondition是线程同步,

[_cityCondition lock];
[_cityCondition wait];
[_cityCondition unlock];

阻塞线程。

    [_cityCondition lock];
    [_cityCondition signal];
    [_cityCondition unlock];

取消阻塞线程.

所以要求阻塞线程是在自线程中进行，解锁可以放在主线程或者是其他子线程中。