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Accessing bytes from NSURLSessionDownloadTask as they are downloaded

In my application, I am currently using NSURLSessionDownloadTask to fetch a file over HTTP.

This class provides a useful delegate interface for tracking its progress and retrieving bytes after the download is complete via NSURLSessionDownloadDelegate , however I have not been able to find any way to access the bytes as they are downloaded (before the download is complete).

Is it possible to access these bytes or do I need to download the file using some other mechanism?

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3 answers


If you need access to the bytes when loading them, you must use a data task, not a task load. And if you then implement the methods NSURLSessionDataDelegate

(specifically didReceiveData

), you can access the bytes as you load them.



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You can use the following method to access data as it gets:



-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
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@ C6Silver's answer is a method in NSURLSessionDataDelegate , not NSURLSessionDownloadDelegate . Here's the way you need to implement:

- (void)URLSession:(NSURLSession *)session
      downloadTask:(NSURLSessionDownloadTask *)downloadTask
      didWriteData:(int64_t)bytesWritten
      totalBytesWritten:(int64_t)totalBytesWritten
      totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite;

You can use a parameter totalBytesWritten

to access the data you want.

Edit . I didn't understand this question.

You will have to use NSURLSessionDataTask and not DownloadTask and then use the delegate method in NSURLSessionDataDelegate :

- (void)URLSession:(NSURLSession *)session
      dataTask:(NSURLSessionDataTask *)dataTask
didReceiveData:(NSData *)data;

This will allow you to access the data as you receive it.

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