Adding delegate to IBDesignable class causes UI not to render

Question

I have a IBDesignable class I am working on, and I have noticed that if I try to add a protocol to the class, it causes an error "Failed to render and update autolayout status"

If I take the protocol out, it works fine, however for some of the functions I will be trying to create, this would be very useful. Example code you can use to recreate the error

import UIKit

protocol TestProtocol {}

@IBDesignable class TestDesignableButton: UIButton {        
    var delegate: TestProtocol?
}

Does anyone know what causes this? And do you know if there is a way around this issue?

Thanks in advance

Answer 1

Change your protocol declaration to:

@objc protocol TestProtocol {}

Here it is, working in my tests (I changed your code a little, but not much — just enough make sure we have the bare bones working). Note that designable button is in fact green; it wouldn't be if the IBDesignable code were not working. Also it says "Up to date" in the inspector at the right.