SwiftUI button viewmodel example for Lessons in SwiftUI blog post (first example)

swiftui-buttons-viewmodel-example.swift

struct ButtonViewModel {    
    // ...
    
    // MARK: Style
    
    var disabledStyle: ButtonType.Style {
        return inverse ? type.disabledInverseStyle : type.disabledStyle
    }

    var selectedStyle: ButtonType.Style {
        return inverse ? type.selectedInverseStyle : type.selectedStyle
    }

    var style: ButtonType.Style {
        return inverse ? type.inverseStyle : type.style
    }
    
    // MARK: Sizing
    
    var cornerRadius: CGFloat {
        return size.cornerRadius
    }

    var height: CGFloat {
        return size.height
    }
    
    // ...
}