facebook login error at ios - objective-c

Question

i'm new at iOS, and i want to do a facebook login for my app.
i tried a lot with the new ios sdk of facebook. but i'm getting error.
the code is
-(IBAction)logIn:(id)sender;
{
AppDelegate *appdelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
[appdelegate sessionOpener];
FBRequest *me = [FBRequest requestForMe];
[me startWithCompletionHandler: ^(FBRequestConnection *connection,
NSDictionary<FBGraphUser> *my,
NSError *error) {
NSLog(#"id %#", my.id);
NSLog(#"name %#", my.first_name);
greet.text = my.first_name;//this is a label to show the name
user.userID = my.id;//this is a FBProfilePictureView to show
}];
[UIView transitionFromView:self.view
toView:userPage
duration:0.5
options:(UIViewAnimationOptionTransitionFlipFromRight | UIViewAnimationOptionTransitionFlipFromLeft)
completion:NULL]; }
`
and sessionOpener is;
-(void) sessionOpener{
[FBSession sessionOpenWithPermissions:nil
completionHandler:^(FBSession *session,
FBSessionState status,
NSError *error) {
// session might now be open.
}];
}
now the errors i get is;
when i first log in to app after logging in the values return null
and i get http 400 error.
but after logged in when i run app second time it gets the info true and prints my name.
my simulator iphone 5.1 simulator

Answer 1

Try creating the session object and add it to the request:
NSArray *permissions = [[NSArray alloc] initWithObjects:
#"email",
#"publish_stream"
nil];
FBSession facebook_session = [[FBSession alloc] initWithPermissions:permissions];`
[[[FBRequest alloc] initWithSession:facebook_session graphPath:#"me"] startWithCompletionHandler:
^(FBRequestConnection *connection,
NSDictionary<FBGraphUser> *user,
NSError *error) {
if (!error) {
// get the data from user object
}else {
NSLog(#"Error: %#",error);
}
}];`