How to make NSURLConnection file download work? - iphone

Question

I have a ViewController declared as:
#interface DownloadViewController : UIViewController
<UITableViewDataSource, UITableViewDelegate>
and I want to use NSURLConnection to download files. NSURLConnection simply "doesn't start", the delegate methods don't work (for example connection:didReceiveResponse is never called) . I noticed in some sample code that the class was subclassing NSObject instead of UIViewController.
How do I combine it? I want to use ViewController methods but then I can't use NSURLConnection.
It's not so easy to find a fully explained example how to download file with NSURLConnection. Everyone only concentrates on the easy methods like didReceiveResponse.

Answer 1

Using a UIViewController instead of an NSObject should not be your problem here !
I'm using a NSURLConnection in an UIViewController with no issue !
Here is a part of my code (not sure it will compile as it is) :
//
// MyViewController.h
//
#import <Foundation/Foundation.h>
#interface MyViewController : UIViewController {
#protected
NSMutableURLRequest* req;
NSMutableData* _responseData;
NSURLConnection* nzbConnection;
}
- (void)loadFileAtURL:(NSURL *)url;
#end
-
//
// MyViewController.m
//
#import "MyViewController.h"
#implementation MyViewController
- (void)loadView {
// create your view here
}
- (void) dealloc {
[_responseData release];
[super dealloc];
}
#pragma mark -
- (void)loadFileAtURL:(NSURL *)url {
// allocate data buffer
_responseData = [[NSMutableData alloc] init];
// create URLRequest
req = [[NSMutableURLRequest alloc] init];
[req setURL:_urlToHandle];
nzbConnection = [[NSURLConnection alloc] initWithRequest:req delegate:self startImmediately:YES];
[req release];
req = nil;
}
#pragma mark -
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
// Append data in the reception buffer
if (connection == nzbConnection)
[_responseData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
if (connection == nzbConnection) {
[nzbConnection release];
nzbConnection = nil;
// Print received data
NSLog(#"%#",_responseData);
[_responseData release];
}
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
// Something went wrong ...
if (connection == nzbConnection) {
[nzbConnection release];
[_responseData release];
}
}
#end
If you plan to download large files, consider storing the received packets in a file instead of storing it in memory !

Answer 2

If you're having problems, you could consider using the well regarded ASIHTTPRequest library to manage your download. It takes care of everything for you.
For example, just 2 lines will do it.
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDownloadDestinationPath:fullPathOfWhereToStoreFile];

Answer 3

Use "NSURLConnection asynchronously" search for the term and you'll find source. Or just NSURLConnection.
For example:
NSURLConnection NSURLRequest proxy for asynchronous web service calls
Using NSURLConnection from apple with example code
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