Fetch Facebook friend list in ios

How do we fetch the Facebook friend list for invitation by application.

I am using this code for fetch the friend list but it shows nothing despite FBSDLLog

Code [FBRequestConnection startWithGraphPath:@"me/friends" completionHandler:^(FBRequestConnection *connection,id result, NSError *error ) { }];

FBSDKLog: Error for request to endpoint 'me/friends': An open FBSession must be specified for calls to this endpoint.

Kindly suggest me how can we do this. i am using SDK below 4.0