多线程之NSThread

- (void)viewDidLoad {
    [super viewDidLoad];
    
    
    //启动线程，downloadImage为线程执行的方法，url为传入参数
    NSURL  *url ;
   [NSThread detachNewThreadSelector:@selector(downloadImage:) toTarget:self withObject:url];
}

- (void)downloadImage:(NSString*)url
{
    //1执行下载
    
    //下载结束，刷新
    [self performSelectorOnMainThread:@selector(fillPhoto) withObject:nil waitUntilDone:NO];
}

- (void)fillPhoto
{
  //更新界面
}