ios后台运行

- (void)run

{

    UIApplication *application = [UIApplication sharedApplication];

    __block UIBackgroundTaskIdentifier background_task;

    background_task = [application beginBackgroundTaskWithExpirationHandler: ^ {

        [self hold];

        [application endBackgroundTask: background_task];

        background_task = UIBackgroundTaskInvalid;

    }];

    

}

- (void)hold

{

    _holding = YES;

    while (_holding) {

        [NSThread sleepForTimeInterval:1];

        CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, TRUE);

    }

}

- (void)stop

{

    _holding = NO;

    DLog(@"end");

}

在applicationDidEnterBackground里面调用run方法