ios ASI 断点下载

//1.创建请求对象
     NSURL *url=[NSURL URLWithString:@"在这里输入你的下载链接"];
     ASIHTTPRequest *request=[ASIHTTPRequest requestWithURL:url];
     
     //2.设置下载文件保存的路径
     NSString *cachepath=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)lastObject];
     NSString *filename=[cachepath stringByAppendingPathComponent:@"video.zip"];
     request.downloadDestinationPath=filename;
     NSLog(@"%@",filename);
     
     //3.设置下载进度的代理
     request.downloadProgressDelegate=self.progress; // 这里别忘了签代理<ASIProgressDelegate>
     
     //4.发送网络请求（异步）
     [request startAsynchronous];

    // 5.断点下载:
     request.allowResumeForFileDownloads=YES;

     //6.下载完毕后通知
     [request setCompletionBlock:^{
         NSLog(@"文件已经下载完毕");
     }];