Question

Developing an app for iOS, I need to know how to have instanced and available an object created when user authenticates.

I am using OAuth2 method properly implementing gtm-oauth2 framework. The user entries, sees the login form displayed in a web view and correctly authenticates. In that moment, as detailed in the documentation, I go like this:

if (error != nil){
    // Do whatever to control the error
}
else
{
    // Authentication succeeded

    // Assign the access token to the instance property for later use
    self.accessToken = myAuth.accessToken;
    [myAuth setShouldAuthorizeAllRequests:YES];
    [self setAuth:myAuth];

    // Display the access token to the user
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Authorization Succeeded"
                                                        message:[NSString stringWithFormat:@"Access Token: %@", myAuth.accessToken]
                                                       delegate:self
                                              cancelButtonTitle:@"Dismiss"
                                              otherButtonTitles:nil];
    [alertView show];
}

Later, in the same controller, I use the self.auth object like this to access my API once the user has authenticated:

[request setURL:getCartsURL];
[request setValue:self.accessToken forHTTPHeaderField:@"Authorization"];
[self.auth authorizeRequest:request
          completionHandler:^(NSError *error) {
              NSString *output = nil;
              if (error) {
                  output = [error description];
              } else {
                  // Synchronous fetches like this are a really bad idea in Cocoa applications
                  //
                  // For a very easy async alternative, we could use GTMHTTPFetcher
                  NSURLResponse *response = nil;
                  NSData *data = [NSURLConnection sendSynchronousRequest:request
                                                       returningResponse:&response
                                                                   error:&error];

                  if (data) {
                      // API fetch succeeded
                      output = [[NSString alloc] initWithData:data
                                                     encoding:NSUTF8StringEncoding];

                      SBJsonParser *jsonParser = [SBJsonParser new];

                      // Parse the JSON into an Object
                      id parsed = [jsonParser objectWithString:output];

                      NSArray *arrayResponse = [[NSArray alloc] initWithArray:parsed];

                  } else {
                      // fetch failed
                      output = [error description];
                  }
              }
          }];

So far, I have been using a local instance of self.auth object, what happens to be insufficient if I want to have that object globally accessed from any point of the whole app. Ok for the init view controller, but not for the whole app.

I think I can somehow access this first view controller to get the object anytime I want it. But I guess we have better methods to have it globally instanced and accessible from any point of the app.

Can you please help me with this?

Thanks a lot.

Answer 1

You should use a Singleton. Here is a nice article on how to set one up.