I have a UIViewController I created in my apps storyboard, as well as a custom UIViewController subclass which I added to the project (and is correctly in the compile phase
Click on a different view controller in the storyboard, then click on it's custom class pulldown to confirm the new class is listed, but don't select it. Click back on the new view controller you made and you should see it now listed in its custom class pulldown menu. odd, eh? just forces a refresh I think.
I had to restart XCode 7.3 (7D175)
In my case, I selected the wrong UI.. so I deleted the class file and created a new one and selected the correct parent class
If you still have your problem or for those who could have the same problem:
Make sure to select on your storyboard your "ViewController" instead of your "View" (which is automatically selected when you click on the view in the storyboard). The difference between those two is that when the view controller is selected, a blue rectangle pop up around your app. To be sure to select the view controller, open the document outline and select it directly in your storyboard hierarchy.
In my case, I drag a new TableViewController object to the storyboard, but I add a new file which's subclass is "UIViewController".... Then, I add a file which's subclass is "UITableViewController", problem solved!!
Storyboard is looking for the custom class but physically its no there and its not displaying the custom class name in the list and also not displaying the outlets . Following solution perfectly worked for me.