This class is not key value coding-compliant for the key cancel

Check for the module name under "Identity Inspector". Either module name has to be selected or "Inherit Module from Target" has to be checked. If there are multiple modules, select the appropriate one.

I agree with what Alex Shubin mentioned in his answer, an actionable solution like “look for any connections that don’t exist anymore and delete them”. I was having the same issue and his suggestion fixed that bug. For those who are new to programming, and Xcode like me, a little more information on how to locate the x button in storyboard might be helpful.

Click on the yellow circle at the top of the view controller in storyboard.

Then show the connections inspector in the upper right of the utilities bar. The connections inspector is the menu on the far right, a circle with a right pointing arrow. Click that, and you should see all the connections for that view controller.

I'm including a screen shot of what that looks like in my app.

This means that you have something on your storyboard connected to the IBOutlet called cancel but you don't have this IBOutlet in your class. So compiler can't find Key cancel(it means property) in your class. You should find that button(i think it's a UIButton because of the name) in storyboard, click right mouse button on it and click "x" to delete that connection. Or you might want to delete this button at all. Or you might want to add this IBOutlet to your class.