title: Delegate methods not called when being hidden
body: <p>I have a View Controller that implements some delegate methods from my facebook helper. When tapping on some icon (like icon), my app switches to facebook mobile web to login. After that, it switches back my app, however, the app requires more permissions for writing so facebook mobile web (safari) once again switches. I press OK and the action done.
  However, the delegate methods in my View Controller not called. I debug and can see at that time the facebook action happens, the variable "delegate" is nil.
  My View Controller has something special. Every time returning back from background, it presents another view controller (for sponsor screen). The displaying duration takes around 3s then the Sponsor screen disappears.
  <br>How can I make the delegate methods called?
  <br>In my view controller
  <br><code>[FacebookHelper sharedInstance].fbDelegate = self;
      [[FacebookHelper sharedInstance] likeCommentFacebook:!isLike withCommentID:message.messageID];
  </code>
  <br>In my facebook helper:
  <br>`- (void) likeCommentFacebook:(BOOL)isLike withCommentID:(NSString *)commentID
  {</p>
  
  <pre><code>//- check if we are already processed by the loginCallback
  if (_loginCallbackInvocation == nil) {
      //- create NSInvocation reference to this method
      NSInvocation * nsi = [WKTools invocationWithTarget:self selector:_cmd retainArguments:TRUE argumentAddresses:&amp;isLike, &amp;commentID];
      //- ensure user has been properly identified and process with authentication if required
      [self processLogin:nsi];
  }
  
  //- check if user session is valid
  if ([[FBSession activeSession] isOpen]) {
      if (![self hasPermission:kPublishStream]) {
          NSArray *permissions = [NSArray arrayWithObjects: kPublishStream,nil];
          dispatch_async(dispatch_get_current_queue(), ^{
              [FBSession.activeSession requestNewPublishPermissions:permissions defaultAudience:FBSessionDefaultAudienceEveryone completionHandler:^(FBSession *session, NSError *error) {
                  NSString *requestUrl = [NSString stringWithFormat:@"%@%@", commentID,FB_REQUEST_LIKE];
                  NSMutableDictionary *params = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"", MESSAGE_KEY, nil];
                  //- send request
                  if (isLike == YES) {
                      [self requestGraphAPI:requestUrl parameter:params httpMethod:POST_METHOD];
                  } else {
                      [self requestGraphAPI:requestUrl parameter:params httpMethod:DELETE_METHOD];
                  }
              }];
          });
      } else {
          NSString *requestUrl = [NSString stringWithFormat:@"%@%@", commentID,FB_REQUEST_LIKE];
          NSMutableDictionary *params = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"", MESSAGE_KEY, nil];
          //- send request
          if (isLike == YES) {
              [self requestGraphAPI:requestUrl parameter:params httpMethod:POST_METHOD];
          } else {
              [self requestGraphAPI:requestUrl parameter:params httpMethod:DELETE_METHOD];
          }
      }
  } else {
      if ([self isSessionCachedAndLoaded]) {
          [FBSession.activeSession openWithCompletionHandler:^(FBSession *session, FBSessionState status, NSError *error) {
              if (![self hasPermission:kPublishStream]) {
                  [[NSUserDefaults standardUserDefaults] synchronize];
                  NSArray *permissions = [NSArray arrayWithObjects: kPublishStream,nil];
                  dispatch_async(dispatch_get_current_queue(), ^{
                      [FBSession.activeSession requestNewPublishPermissions:permissions defaultAudience:FBSessionDefaultAudienceEveryone completionHandler:^(FBSession *session, NSError *error) {
                          NSString *requestUrl = [NSString stringWithFormat:@"%@%@", commentID,FB_REQUEST_LIKE];
                          NSMutableDictionary *params = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"", MESSAGE_KEY, nil];
                          DEBUGLog(@"like comment: %@",requestUrl);
  
                          //- send request
                          if (isLike == YES) {
                              [self requestGraphAPI:requestUrl parameter:params httpMethod:POST_METHOD];
                          } else {
                              [self requestGraphAPI:requestUrl parameter:params httpMethod:DELETE_METHOD];
                          }
                      }];
                  });
              } else {
                  NSString *requestUrl = [NSString stringWithFormat:@"%@%@", commentID,FB_REQUEST_LIKE];
                  NSMutableDictionary *params = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"", MESSAGE_KEY, nil];
                  //- send request
                  if (isLike == YES) {
                      [self requestGraphAPI:requestUrl parameter:params httpMethod:POST_METHOD];
                  } else {
                      [self requestGraphAPI:requestUrl parameter:params httpMethod:DELETE_METHOD];
                  }
              }
          }];
      }
  }
  </code></pre>
  
  <p>}`</p>
  
  <p>and in callback method</p>
  
  <p><br><code>if (self.fbDelegate &amp;&amp; [self.fbDelegate respondsToSelector:@selector(likeCommentDidSuccess:)]) {
                      [self.fbDelegate performSelector:@selector(likeCommentDidSuccess:) withObject:dictionary];
                  }</code></p>