Issue in fetching facebook friendlist after application quit in ios9

Question

I had written the below code for fblogin :

 FBSDKLoginManager *fblogin = [[FBSDKLoginManager alloc] init];
    [fblogin logInWithReadPermissions:params fromViewController:viewController handler:^(FBSDKLoginManagerLoginResult *result, NSError *error)
    {
        if (error) {
            // Show process error from facebook
            NSLog(@"Process error");
            completion(nil,error);
        } else if (result.isCancelled) {
            /// At time of done and cancel event
            NSLog(@"Cancelled");
            completion(nil,error);
        } else {
            /// This action come at least one permission allowed user
            NSLog(@"Logged in");
            completion(result,error);
        }
    }];

To fetch the user detail The code which i had written is :

[[[FBSDKGraphRequest alloc] initWithGraphPath:@"me" parameters:@{@"fields": @"picture.type(large), email,birthday,name,gender,first_name, last_name,bio, invitable_friends"}] startWithCompletionHandler:^(FBSDKGraphRequestConnection *connection, id result, NSError *error)
    {

              if(!error)
        {
            completion(result,error);
        }
        else
        {
            completion(nil,error);
        }
    }];

After user login. I am trying to fetch the friendlist (only if) user click invite friend button.

To fetch the friend list the code which i use to fetch friendlist :

   FBSDKGraphRequest *request = [[FBSDKGraphRequest alloc]
                                  initWithGraphPath:@"/me/invitable_friends?limit=5000"
                                  parameters:@{@"fields": @"name,first_name, last_name,invitable_friends"}
                                  HTTPMethod:@"GET"];
    [request startWithCompletionHandler:^(FBSDKGraphRequestConnection *connection,
                                          id result,
                                          NSError *error) {
        // Handle the result
        NSLog(@"result==>%@",result);
    }];

I am getting proper friend list from the above code. Issue is When i quit my application and reopen the application and then try to fetch the friend list again it give me error.

Error which i am getting is :

Error Domain=com.facebook.sdk.core Code=8 "(null)" UserInfo={com.facebook.sdk:FBSDKGraphRequestErrorCategoryKey=0, com.facebook.sdk:FBSDKGraphRequestErrorHTTPStatusCodeKey=400, com.facebook.sdk:FBSDKErrorDeveloperMessageKey=An active access token must be used to query information about the current user., com.facebook.sdk:FBSDKGraphRequestErrorGraphErrorCode=2500, com.facebook.sdk:FBSDKGraphRequestErrorParsedJSONResponseKey={
    body =     {
        error =         {
            code = 2500;
            "fbtrace_id" = BrC8am8ChZ6;
            message = "An active access token must be used to query information about the current user.";
            type = OAuthException;
        };
    };
    code = 400;
}}

Answer 1

I had solved this by writing the below line in my appdelegate:

[[FBSDKApplicationDelegate sharedInstance] application:application didFinishLaunchingWithOptions:launchOptions];

I got this answer from below link : Reliable check for active session on app startup in Facebook iOS SDK v4.0

Thank you SO