NSArray *readPermissions = @[@"email",@"id",@"name"];

    return [FBSession openActiveSessionWithReadPermissions:readPermissions
                                              allowLoginUI:allowLoginUI
                                         completionHandler:^(FBSession *session, FBSessionState state, NSError *error) {
                                             if (error) {
                                                 NSLog (@"Handle error %@", error.localizedDescription);
                                             } else {
                                                 [self checkSessionState:state];
                                             }
                                         }];