Not able to download a file with NSURLRequest - ios

Question

I am just new in IOS development. I've been trying to figure apple documentations. So I read this page:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/URLLoadingSystem/Tasks/UsingNSURLConnection.html#//apple_ref/doc/uid/20001836-BAJEAIEE
and this is what I have done:
NSMutableData *testFileType;
// Create the request.
NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:urlString]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
// create the connection with the request
// and start loading the data
NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
if (theConnection) {
// Create the NSMutableData to hold the received data.
// receivedData is an instance variable declared elsewhere.
testFileType = [[NSMutableData data] retain];
NSLog(#"the connection is successful");
} else {
// Inform the user that the connection failed.
NSLog(#"the connection is unsuccessful");
}
[testFileType setLength:0];
[testFileType appendData:[NSMutableData data]];
Can anyone tell me what am I missing here?

Answer 1

Just creating the NSURLConnection is not enough. You also need to implement the didReceiveResponse and didFinishLoading delegate methods. Without these the connection downloads the file, but you never get to see it.
NSURLConnection sends a didReceiveResponse for every redirection when the headers are received. Then it sends a didReceiveData with some bytes of the file. Those you need to append to your mutable data. Finally you get a didFinishLoading where you know that you have gotten all data. In case of error you get a didFailWithError instead.
Look at the NSURLConnectionDelegate protocol documentation: https://developer.apple.com/library/mac/ipad/#documentation/Foundation/Reference/NSURLConnectionDelegate_Protocol/Reference/Reference.html

Answer 2

you should implement the following delegate methods:
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
NSLog(#"Error: %d %#", [error code], [error localizedDescription]);
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
responseData = [NSMutableData data];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[responseData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
[responseData writeToFile:savePath atomically:YES];
}
here responseData and savePath are instance variables declared with:
NSMutableData *responseData;
NSString *savePath;
and your class must conforms the NSURLConnectionDataDelegate and NSURLConnectionDelegate protocols.
For the code to work you probably want to set savePath to a working path like this
NSString *savePath = [NSTemporaryDirectory() stringByAppendingPathComponent:#"testfile.txt"];
after the download have finished, you can do anything to the file at savePath as you wish.