I'm making a custom keyboard extension in Objective-C for iOS 15+. Originally I designed myCustomInputView and put all my keyboard stuff into it, using constraints for everything. I then would add it as a subview like this: [myCustomKeyboardVC.inputView addSubview:myCustomInputView] and then contain it to .inputView. That mostly worked fine, except that after making and dismissing several I had a bunch of myCustomInputView objects remaining, being referenced by _inputViewContent which isn't being used by a custom keyboard anymore. I saw a suggestion that I should do this instead: myCustomKeyboardVC.inputView = myCustomInputView so that myCustomInputView is assigned directly to the VC's .inputView rather than being a subview of it. But this has problems because I now don't know what to constrain it to, and it runs wider than the screen. (ie, how do I constrain myCustomInputView to the keyboard width)? So I guess my basic question is: must custom UIInputViews be assigned directly to .inputView or can they be a subview of it?