If the TRDiscussionDetailsViewController is your destination view controller, you need to keep it from segue instead of re-instantiate it. I think you should do this:
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:@"communityToDetails"]) {
TRDiscussionDetailsViewController *ddvc = (TRDiscussionDetailsViewController*)segue.destinationViewController;
ddvc.discussionID = selectedDiscussionID;
NSLog(@" discussion id %@", ddvc.discussionID);
}
}
Hope it helps