How to send Asynchronous URL Request?

Question

I would like to know how do I get a return value 1 or 0 only.... back from an URL request asynchronously.

currently I do it in this way:

NSString *UTCString = [NSString stringWithFormat:@"http://web.blah.net/question/CheckQuestions?utc=%0.f",[lastUTCDate timeIntervalSince1970]];
NSLog(@"UTC String %@",UTCString);
NSURL *updateDataURL = [NSURL URLWithString:UTCString];
NSString *checkValue = [NSString stringWithContentsOfURL:updateDataURL encoding:NSASCIIStringEncoding error:Nil];
NSLog(@"check Value %@",checkValue);

this works, however it is blocking my main thread till I got a reply back from the URL, how do I set it so it will do it in a another thread instead of the main thread ?

EDIT: ANSWER I end upcalling my function with this, it works well :)

[self performSelectorInBackground:@selector(shouldCheckForUpdate) withObject:nil];

Answer 1

you can use NSURLConnection class

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
[[[NSURLConnection alloc] initWithRequest:request delegate:self] autorelease];

and handle its response and errors using its delegate methods.

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
- (void)connectionDidFinishLoading:(NSURLConnection *)connection 

You can find implementation of NSURLConnection

• Apple docs: Using NSURLConnection
• How To Use iOS NSURLConnection By Example

Edit: Although NSURLConnection is provided by apple is more recommended way of placing URL request. But I found AFNetworking library very time saving, easy to implement and robust yet simple as third party implementation. You should give it a try.