OptionAsync<T>.Do(Action<T> Some, Action None)

[IlyaVassyutovich]

Good day, fellow engineers.

The following question is about the V4-library

Today I needed to Do some actions on an OptionAsync for both its state variants. There is no out-of-the-box solution for this, or I couldn't find it. So I've tried to create my own extension method for this use case. This is what I've come up with:

public static OptionAsync<T> Do<T>(
	this OptionAsync<T> option,
	Action<T> some,
	Action none) where T : class
{
	return OptionAsync<T>.OptionalAsync(DoCore());

	async Task<T?> DoCore()
	{
		return await option.MatchUnsafe<T?>(
			t =>
			{
				some(t);
				return t;
			},
			() =>
			{
				none();
				return null;
			});
	}
}

This extension works for me as intended, but there is a big caveat — look at the generic constraint. I can't use this extension with value types. And if I try to drop the constraint, factories of OptionAsync always produce Some since inside these factories, code is written like if (value == null) ? none : some.

Is there a better way that I'm not seeing?

Thanks!

[StefanBertels]

Quick solution:

You can create two extensions methods -- one having where T : class and one having where T: struct as constraint. They can have the same name if they are in different static extension classes (but maybe keep them in the same file).

[harrhp]

you can return original OptionAsync from Match since you are not changing it's bound value. or you can use Prelude.None instead of null and Prelude.SomeAsync to return new OptionAsync from Match

option.Match(
	t =>
	{
		some(t);
		return option;
	},
	() =>
	{
		none();
		return option;
	})

[IlyaVassyutovich]

@harrhp Your Match will return Task<OptionAsync<T>>, what am I supposed to do with it then if I need to return plain OptionAsync<T> from my extension?

I suppose Match here is wrong in any way since it elevates Option to another level.

[harrhp]

sorry, was writing without an ide. this should work as expected

public static OptionAsync<T> Do<T>(
        this OptionAsync<T> option,
        Action<T> some,
        Action none)
    {
        return option.Match(
            t =>
            {
                some(t);
                return Prelude.Some(t);
            },
            () =>
            {
                none();
                return Prelude.None;
            }).ToAsync();
    }