SwiftUI button viewmodel example for Lessons in SwiftUI blog post (2nd example)

swiftui-buttons-viewmodel-example-2.swift

struct ButtonViewModel {
    // ...
    
    // MARK: State Styles
    
    func backgroundColor(for isEnabled: Bool, isPressed: Bool) -> Color {
        let styles = buttonTypeStyle(for: isEnabled, isPressed: isPressed)
        return styles.backgroundColor.color.opacity(styles.buttonOpacity)
    }

    func borderColor(for isEnabled: Bool, isPressed: Bool) -> Color {
        let styles = buttonTypeStyle(for: isEnabled, isPressed: isPressed)
        return styles.borderColor.color
    }

    func foregroundColor(for isEnabled: Bool, isPressed: Bool) -> Color {
        let styles = buttonTypeStyle(for: isEnabled, isPressed: isPressed)
        return styles.textColor.color
    }

    func scaleEffect(for isEnabled: Bool, isPressed: Bool) -> CGFloat {
        guard isEnabled else { return 1.0 }
        return isPressed ? 0.99: 1.0
    }
    
    // MARK: State Helpers

    func buttonTypeStyle(for isEnabled: Bool, isPressed: Bool) -> ButtonType.Style {
        return isPressed ? buttonTypeStyle(forIsPressed: isPressed) : buttonTypeStyle(forIsEnabled: isEnabled)
    }

    func buttonTypeStyle(forIsEnabled isEnabled: Bool) -> ButtonType.Style {
        guard let iconStyle = self.iconStyle else {
            return isEnabled ? style : disabledStyle
        }
        return isEnabled ? iconStyle : disabledStyle
    }

    func buttonTypeStyle(forIsPressed isPressed: Bool) -> ButtonType.Style {
        guard let iconStyle = self.iconStyle else {
            return isPressed ? selectedStyle : style
        }
        return isPressed ? type.iconOnlySelectedStyle : iconStyle
    }
}