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

    // this doesn't have a warning
    @IBInspectable var topIndicatorFillColor: UIColor? {
        didSet {
            topIndicator.fillColor = topIndicatorFillColor?.cgColor
        }
    }
}

Is there a way to get rid of it ?

score 35 · Accepted Answer · edited Jun 04 '21 at 17:33

35

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.

edited Jun 04 '21 at 17:33

ScottyBlades

12,189
5
77
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answered Sep 03 '17 at 14:27

I still get the warning, even after I remove the optional and add default value. – Adrian Sep 03 '17 at 14:43
Then there has to be something (besides a closing bracket) different between the code you posted and your project code. My *error* (which may be an indication) disappeared. I'll edit my answer with that code. – Sep 03 '17 at 14:52
it's ok now, they are gone. I guess it took some time for Xcode to update – Adrian Sep 03 '17 at 14:55
Almost added the edit. Guess that's overwork. Glad I could help. – Sep 03 '17 at 14:56
And what if I still need the optional property? :-) – Vitya Shurapov Oct 12 '17 at 13:00
1

I'd probably *try very hard* to not make an optional IB property (since `IBDesignable` is meant for *visible* properties, shouldn't they have a default?), but maybe try defaulting to `nil`? I'm not stating that such a thing would work, but it may be worth a shot. – Oct 12 '17 at 14:32

score 9 · Answer 2 · answered Nov 23 '17 at 05:27

9

Below two points might helps you

As there is no concept of optional in objective c, So optional IBInspectable produces this error. I removed the optional and provided a default value.
If you are using some enumerations types, then write @objc before that enum to remove this error.

answered Nov 23 '17 at 05:27

Aaban Tariq Murtaza

1,155
14
16

> As there is no concept of optional in objective c it is not exactly true. Classes is ObjC are nullable by design. UIColor is a class. So, correct equivalent of ObjC's `UIColor` in Swift is `UIColor?` – Krypt May 17 '19 at 18:21

Shakeel Ahmed · Answer 3 · 2019-07-30T09:04:54.013

5

Swift - 5

//Change this with below
@IBInspectable public var shadowPathRect: CGRect!{
    didSet {
        if shadowPathRect != oldValue {
            setNeedsDisplay()
        }
    }
}

To

@IBInspectable public var shadowPathRect: CGRect = CGRect(x:0, y:0, width:0, height:0) {
    didSet {
        if shadowPathRect != oldValue {
            setNeedsDisplay()
        }
    }
}

edited Jul 30 '19 at 09:04

answered May 13 '19 at 05:26

Shakeel Ahmed

5,361
1
43
34

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

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