How to get attribute from AttributeContainer in UIKit and assign it to some variable

I create next subclass:

import UIKit

class Button: UIButton {

    override func updateConfiguration() {
        var config = configuration ?? UIButton.Configuration.plain()

        let color = config.attributedTitle?.foregroundColor

        switch state {
        case .normal:
            config.attributedTitle?.foregroundColor = color.withAlphaComponent(1)

        case .highlighted:
            config.attributedTitle?.foregroundColor = color.withAlphaComponent(0.5)

        default:
            break
        }

        configuration = config
    }
}

I this class I want to get foregroundColor from attributedTittle(AttributedString class) to assign it later with alphaComponent to different button states, BUT I can't get any attribute from attributedString(or AttributedContainer) in updateConfiguration method.
In my example property "color" is always nil (actually all other attribute are nil if I try get them) and the return type of "color" is:

AttributeScopes.SwiftUIAttributes.ForegroundColorAttribute.Value?

And I get this error when try to assign color back to attributedString:

 Value of type 'AttributeScopes.SwiftUIAttributes.ForegroundColorAttribute.Value?' (aka 'Optional<Color>') has no member 'withAlphaComponent'

So why I can't get any attributes from AttributedString here?

Solution

It appears that the compiler is prioritising the foregroundColor in the SwiftUIAttributes attribute scope. You can force it to choose the UIKit one by specifying the type of color.

let color: UIColor? = config.attributedTitle?.foregroundColor

Alternatively, access the uiKit attribute scope directly:

let color = config.attributedTitle?.uiKit.foregroundColor

Note that this should be an optional type, so you should unwrap it when you use withAlphaComponent:

config.attributedTitle?.foregroundColor = color?.withAlphaComponent(1)
                                               ^