Getting the NSURLConnection delegate callback into the right thread - objective-c

Question

I can't seem to get a Delegate callback to work when I thread my code. I am trying to call a remote server using NSURLConnection to get an access_token. The access_token is received in connection:didReceiveResponse: delegate. This is not a problem until I thread it. I thought I was passing the correct objects for my delegates, but it does not reach connection:didReceiveResponse:
Can anyone see why connection:didReceiveResponse: in LoginViewController does not get called when I thread the call? Thanks.
LoginViewController.m
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
NSString *access_token = [self getTokenFromResponse: response];
[self.delegate didGetAccessToken:access_token];
}
- (void)fetchAccessTokenNoUI
{
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString: #"www.mysite.com"]];
[NSURLConnection connectionWithRequest:request delegate:self];
}
AccessToken.h
#interface AccessToken : NSObject
#property (atomic, strong) LoginViewController *loginViewController; // doing this to try to keep it persistent
- (void) fetchAccessTokenWithDelegate: (id <LoginDelegate>)delegate;
#end
AccessToken.m
- (void) fetchAccessTokenWithDelegate: (id < LoginDelegate >)delegate
{
dispatch_queue_t downloadQueue = dispatch_queue_create("Fetch access_token queue", NULL);
dispatch_async(downloadQueue, ^ {
// this works fine if I don't do it in a queue
self.loginViewController = [[LoginViewController alloc] init];
self.loginViewController.delegate = delegate;
[self.loginViewController fetchAccessTokenNoUI];
});
dispatch_release(downloadQueue);
}
CallingClass.m
- (void)didGetAccessToken:(NSString *)access_token
{
if (!access_token)
{
LoginViewController *userProfileViewController = [[LoginViewController alloc] init];
userProfileViewController.delegate = self;
[self.navigationController pushViewController:userProfileViewController animated:YES];
}
}
- (IBAction)favourite:(id)sender
{
AccessToken *accessToken = [[AccessToken alloc] init];
[accessToken fetchAccessTokenWithDelegate:self];
}

Answer 1

So after some more research, I found the solution.
I don't actually need AccessToken.h/m. I thought that the NSURLConnection call would block my UI thread. But NSURLConnection connectionWithRequest:delegate: is automatically run in a separate thread.
So all I have to do is delete AccessToken.h and AccessToken.m. Then, in CallingClass.m, I change favourte: to
- (IBAction)favourite:(id)sender
{
LoginViewController *loginViewController = [[LoginViewController alloc] init];
[loginViewController fetchAccessTokenWithDelegate:self];
}
That's it! Don't need to dispatch_queue_t at all.

Answer 2

Have you put stubs to implement the required protocol methods,
-(void)connectionDidFinishLoading:(NSURLConnection *)connection;
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;
Because I had a similar problem which went away after implementing them.