Get all derived classes from a base class

[obfuscate]

Hello there!

By some reasons I want to collect all derived class of a specific base class. At this moment, I found only such solution but tbh I don't like it:

auto base = entt::resolve<Base>();
for (auto&& [id, type] : entt::resolve())
{
	if (type.can_cast(base))
	{
		// do some logic here.
	}
}

Is there a way do it more properly avoiding iterating over ALL registered classes?

for example, RTTR allows to do it like this:

for (auto child : rttr::type::get<Base>().get_derived_classes())
{
	// do some logic here.
}

[skypjack]

There isn't (yet?) something similar in meta, I'm sorry. I've never had the need to find all derived classes actually. What's the use case?
If you want a quick solution, you can use custom data and bind a map yo the base class on your own, then register derived classes there.
It's not a built-in solution, but it gets the job done in the meantime without having to iterate all types.

[obfuscate]

Hello, thanks for you answer!

What's the use case?

So, I'll try to explain: for example I decided to use argh (the library for handling command line input), it has API: argh::parser::add_param("-param");. So, such parameters I want to obtain from some classes which might be added from other dlls (that's why I think that the solution via a map won't work). That's why I try to use some kind of reflection (in the RTTR it could be easily done):

// Registration (for example in some custom dll):
reflection::Integration<RenderDocIntegration>("RenderDocIntegration")
	.cli({"-rdoc"});

// Using:
auto base = rttr::type::get<Base>();
for (auto child : base.get_derived_classes())
{
	if (auto cliMeta = child.get_metadata(CLIMetaHandle))
	{
		const auto& cli = cliMeta.get_value<CLIArgs>();
		for (auto param : cli)
		{
			arghParser.add_param(std::string(param));
		}
	}
}

Now, I'm looking at entt's meta, trying to port my RTTR code on it and I'm a little bit struggling now with it:)

[skypjack]

Yeah, to be fair, rttr uses an invasive macro that adds some functions to user classes, which is something I want to avoid.
If you have any suggestions on how to get a similar result without an invasive solutions, I'm more than willing to discuss it.
Otherwise, a custom mode solution in the user space is the only way to go I guess. 🤔