以视频下载为例：
在做下载功能时，有时候会遇到后台给提供了非视频资源的下载链接，
如下方法可将非视频资源过滤掉
#pragma mark - NSURLSessionDelegate
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSHTTPURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler {
NSString *miniType = response.MIMEType; //有时后台错误，给的下载链接为非视频
if(download && download.DownloadState == PVR_DOWNLOAD_RUN){
if ([NSString isEmpty:miniType] || ![miniType hasPrefix:@"video"]) {
NSLog(@"资源地址为空，或不是视频类资源");
}
