图片下载

//从网络上下载图片

NSString *qrCodeURL = [NSString stringWithFormat:@"http://api.fanggw.cn/index.php/Mobile/Index/get_qrcode?mobile=%@&pwd=%@",phone,secret];

    NSURL *url = [NSURL URLWithString:qrCodeURL];

    [_qrCodeImage sd_setImageWithURL:url completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {

    }];

图片下载

原文：http://blog.csdn.net/huanghaiyan_123/article/details/45309005