How to download a large file with the iPhone SDK and avoid memory usage issues?

Question

I'm using the NSURLConnection class to download a large file in my iPhone application, but it crashes every so often because it's using too much memory. I'm doing the usual NSURLConnection usage, to append the received data to a NSMutableData object.

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {     [self.fileData appendData:data]; } 

Then after I finish downloading the whole file, I save it to a local temporary file, and read it as a mapped file like this:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {     // save the downloaded data into a temporary file     NSString *tempPath = NSTemporaryDirectory();     NSString *tempFile = [tempPath stringByAppendingPathComponent:@"temp.pdf"];     [self.fileData writeToFile:tempFile atomically:YES];     NSData *mappedData = [NSData dataWithContentsOfMappedFile:tempFile];      NSURL *baseURL = [NSURL URLWithString:@"http://mydomain.com"];     [webView loadData:mappedData MIMEType:@"application/pdf" textEncodingName:@"UTF-8" baseURL:baseURL]; } 

What can I improve here to avoid these memory usage problems?

Answer 1

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse*)response {      filename = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:save_name]; // filename is in .h file      [[NSFileManager defaultManager] createFileAtPath:filename contents:nil attributes:nil];         file = [[NSFileHandle fileHandleForUpdatingAtPath:filename] retain];// file is in .h   //if (file)     { // //      [file seekToEndOfFile]; //  }  }  - (void)connection:(NSURLConnection *)connection didReceiveData:(NSD ata *)data {   if (file)  {           [file seekToEndOfFile];      } [file writeData:data];   }  - (void)connectionDidFinishLoading:(NSURLConnection*)connection {   [file closeFile];   } 

Answer 2

If it's that large, why not write it to the file as it comes in, rather than keeping it in an NSData object?