title: How to get all facebook friends using ios sdk?
body: <p>i want to get all friend list of facebook friend but didn't getting list.</p>
  
  <pre><code>if (!FBSession.activeSession.isOpen) {
      // if the session is closed, then we open it here, and establish a handler for state changes
      [FBSession openActiveSessionWithReadPermissions:@[@"public_profile", @"user_friends"] allowLoginUI:YES completionHandler:^(FBSession *session,FBSessionState state,NSError *error) {
          if (error)
          {
              UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error"
              message:error.localizedDescription delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
              [alertView show];
          }
          else if (session.isOpen)
          {
              [self pickFriendsButtonClick:sender];
          }
      }];
      return;
  }
  
  if (self.friendPickerController == nil) {
      // Create friend picker, and get data loaded into it.
      self.friendPickerController = [[FBFriendPickerViewController alloc] init];
      self.friendPickerController.title = @"Pick Friends";
      self.friendPickerController.delegate = self;
  }
  
  [self.friendPickerController loadData];
  [self.friendPickerController clearSelection];
  
  [self presentViewController:self.friendPickerController animated:YES completion:nil];
  </code></pre>
  
  <p>i use this code to get all FB friends but it not work for me.</p>