IOS Facebook active status and invite

Question

I have downloaded the latest FB Sdk and successfully implemented the login feature. Now if i try to check if the user is active using the below code,

if (FBSession.activeSession.isOpen)

It give Use of Undeclared Identifier FBSession. Also, i want to invite friends for my app. Tried using

[FBSWebDialogs presentRequestsDialogModallyWithSession:nil
         message:NSLocalizedString(@"FBinviteMessage", nil)
         title:nil
         parameters:nil
         handler:^(FBWebDialogResult result, NSURL *resultURL, NSError *error) {}
         ];

But, got the error 'Use of undeclared identifier FBSWebDialogs'. Have included the following headers.

#import <FBSDKCoreKit/FBSDKCoreKit.h>
#import <FBSDKLoginKit/FBSDKLoginKit.h>
#import <FBSDKShareKit/FBSDKShareKit.h>

Please suggest where am i going wrong!