Question

I’m trying to make an enum of strings. Here’s what I’ve got so far,

private class TypedEnum<T> : IEnumerable<T>
{
    public IEnumerator<T> GetEnumerator()
    {
        return GetType().GetFields().Where(f => f.IsLiteral).Select(f => f.GetValue(null)).OfType<T>().GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}

private static class Combinators : TypedEnum<char>
{
    public const char DirectChild = '>';
    public const char NextAdjacent = '+';
    public const char NextSiblings = '~';
    public const char Descendant = ' ';
}

But there are two problems with this. (1) It won’t compile because Combinators is static… I can remove that and hide the c’tor though. (2) It’s not enumerable unless I instantiate it, which I don’t need nor want to do. What are my options? Forget about making it enumerable?

---

I think this is as close as I can get

public struct Combinators
{
    public const char DirectChild = '>';
    public const char NextAdjacent = '+';
    public const char NextSiblings = '~';
    public const char Descendant = ' ';

    public static IEnumerable<char> ToEnumerable()
    {
        return typeof(Combinators).GetFields().Where(f => f.IsLiteral)
            .Select(f => f.GetValue(null)).OfType<char>();
    }
}

But I wish I could put that ToEnumerable() method in a subclass 🙁

Answer 1

Hah! Solved it!

public class TypedEnum<TBase, TValue>
{
    public static IEnumerable<TValue> ToEnumerable()
    {
        return typeof (TBase).GetFields(BindingFlags.Public | BindingFlags.Static)
            .Select(f => f.GetValue(null)).OfType<TValue>();
    }

    public static TValue[] ToArray()
    {
        return ToEnumerable().ToArray();
    }

    public static string Pattern
    {
        get
        {
            return string.Format("(?:{0})", string.Join("|", ToEnumerable().Select(c => Regex.Escape(c.ToString()))));
        }
    }
}

public class Combinators : TypedEnum<Combinators, char>
{
    public const char DirectChild = '>';
    public const char NextAdjacent = '+';
    public const char NextSiblings = '~';
    public const char Descendant = ' ';
}

Just have to pass the class itself as a type to TypedEnum.