How to Use the Appropriate Color Class For the Current Platform

How do you use the appropriate color class for the current platform?

Use conditional compilation and type aliases:

#if os(OSX)
    typealias Color = NSColor
    typealias Image = NSImage
#else
    typealias Color = UIColor
    typealias Image = UIImage
#endif

Then use Color instead of UIColor or NSColor:

self.gameView!.backgroundColor = Color(red: 0, green: 0.2, blue: 0.5, alpha: 1)

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Edit 2016-01-17: As DDPWNAGE noted above, Apple has created SKColor with basically the same definition.

Universal class for Mac OS and iOS

You should be able to use typealias for the color class, like this:

#if os(iOS)
    typealias XColor = UIColor
#elseif os(OSX)
    typealias XColor = NSColor
#endif

func myFunc(color: XColor?) {
    self.myFuncX(color)
}

The idea is to limit conditional compile to a type definition for XColor, and then using that type alias in place of UIColor or NSColor, as required on the particular system.

how to have the color of the windows theme MAUI

UISettings Class could be used to get current system color in windows platform , the point is how to convert Windows.UI.Color to Microsoft.Maui.Graphics.Color .

Sample code

#if WINDOWS
    var uiSettings = new Windows.UI.ViewManagement.UISettings();
    var color = uiSettings.GetColorValue(UIColorType.Accent);

    //change button color with system theme color
    button.BackgroundColor = Microsoft.Maui.Graphics.Color.Parse(color.ToString());
#endif

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And if you want to change the color dynamically according to system theme, take a look at Application.Current.RequestedThemeChanged event ,it is used to to detect the change of system theme .

Notice: The following event is only triggered when switching between light/dark theme .

Sample code

Application.Current.RequestedThemeChanged += (s, a) =>
{
#if WINDOWS
    var uiSettings = new Windows.UI.ViewManagement.UISettings();
    var color = uiSettings.GetColorValue(UIColorType.Accent);

    //change button color with system theme color
    button.BackgroundColor = Microsoft.Maui.Graphics.Color.Parse(color.ToString());
#endif
};

Use a parent class init inside of a class protocol that conforms to a class

Here's how I would do it. No protocol needed! Just extend SKSpriteNode and inherit:

extension UIColor {
    static var image : UIColor {
        UIColor(red: 1, green: 1, blue: 1, alpha: 0)
    }
}
extension SKTexture {
    convenience init(_ s:String) {
        self.init(imageNamed:s)
    }
}

extension SKSpriteNode {
    @objc class var size: CGSize { .zero } // override me for subclass
    convenience init(_ name: String) {
        self.init(texture: SKTexture(name), color: .image, size: Self.size)
    }
}

// example
class Platform: SKSpriteNode {
    override class var size: CGSize {
        CGSize(width: 300, height: 50)
    }
}

And now you are able to say let p = Platform("yoho"), which is what I believe we were aiming at.

Creating an Array of CGColors from an Array of UIColors or NSColors

You could do:

extension _ArrayType where Generator.Element == UIColor {
    func CGColors() -> [CGColorRef] {
        var cgColorArray: [CGColorRef] = []

        for color in self {
            cgColorArray.append(color.CGColor)
        }

        return cgColorArray
    }
}

Use it like so:

let colors: [UIColor] = [UIColor.redColor(), UIColor.orangeColor()]
colors.CGColors()

Repeat for NSColor.

How can I get color-int from color resource?

You can use:

getResources().getColor(R.color.idname);

Check here on how to define custom colors:

http://sree.cc/google/android/defining-custom-colors-using-xml-in-android

EDIT(1):
Since getColor(int id) is deprecated now, this must be used :

ContextCompat.getColor(context, R.color.your_color);

(added in support library 23)

EDIT(2):

Below code can be used for both pre and post Marshmallow (API 23)

ResourcesCompat.getColor(getResources(), R.color.your_color, null); //without theme

ResourcesCompat.getColor(getResources(), R.color.your_color, your_theme); //with theme

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