Question

I have a class Color that holds values for the red, green, blue, and alpha channels of a color. The class constructor lets you create a new color by specifying values for the four channels. However, for convenience, I would also like to have some “premade” colors available for the programmer. For example instead of having something like

DrawBox(new Color(255, 0, 0));

you would be able to say

DrawRectangle(Color::Red);

Where Color.Red is an instance of Color that lives inside the Color class. How can I declare these instances of Color inside the Color class? I’m sure there’s a name for this technique, but I had no idea what search terms to use when I was looking for help online.

I’m not using any built-in or publicly-available classes or libraries because this is part of a personal exercise in creating a basic graphics stack.

Thanks for your help!

Answer 1

First of all, avoid using new. You could use Color as simple value-type.

Now as an answer to your question, yes, you can do that as:

//color.h

typedef unsigned char byte;

class Color
{
    public:
        //declaration
        const static Color Red;
        const static Color Green;
        const static Color Blue;
    public:

       Color(byte red, byte green, byte blue);
};

//define the static members in color.cpp file
#include "color.h"

const Color Color::Red(255,0,0);
const Color Color::Green(0,255,0);
const Color Color::Blue(0,0,255);

Then use Color::Red as you want to use.