NSData dataWithContentsOfURL for twitter图片返回nil，同样的东西适用于instagram

Question

我试图显示推特图片但是dataWithContentsOfString返回零，当相同的确切的东西适用于Instagram照片网址时。当我使用实际的url而不是从nsdictionary

获取它时，它可以工作

NSString *twitterString = @"http://pbs.twimg.com/media/BYWHiq1IYAAwSCR.jpg"

但不喜欢这个

if ([post valueForKeyPath:@"entities.media.media_url"]) {
        NSString *twitterString = [NSString stringWithFormat:@"%@", [post valueForKeyPath:@"entities.media.media_url"]];
        NSURL *twitterPhotoUrl = [NSURL URLWithString:twitterString];
        dispatch_queue_t queue = kBgQueue;
        dispatch_async(queue, ^{
            NSData* data = [NSData dataWithContentsOfURL:twitterPhotoUrl];
            UIImage *image = [UIImage imageWithData:data];

            dispatch_sync(dispatch_get_main_queue(), ^{
                [streamPhotoArray replaceObjectAtIndex:indexPath.row withObject:image];
                cell.twitterPhoto.image = image;
            });
        });
    }