How to fix “'@IBInspectable' attribute is meaningless on a property that cannot be represented in Objective-C” warning

Question

In Xcode 9 and Swift 4 I always get this warning for some IBInspectable properties:

    @IBDesignable public class CircularIndicator: UIView {
          


        

Answer 1

Maybe.

The exact error (not warning) I got when doing a copy/paste of class CircularIndicator: UIView is:

Property cannot be marked @IBInspectable because its type cannot be represented in Objective-C

I resolved it by making this change:

@IBInspectable var backgroundIndicatorLineWidth: CGFloat? {  // <-- warning here
    didSet {
        backgroundIndicator.lineWidth = backgroundIndicatorLineWidth!
    }
}

To:

@IBInspectable var backgroundIndicatorLineWidth: CGFloat = 0.0 {
    didSet {
        backgroundIndicator.lineWidth = backgroundIndicatorLineWidth!
    }
}

Of course, backgroundIndicator is undefined in my project.

But if you are coding against didSet, it looks like you just need to define a default value instead of making backgroundIndicatorLineWidth optional.