Add computed attributes / properties to userdata objects?

[natinusala]

I have userdata registered as objects using the metatable["__index"] = metatable technique. I can register methods by adding them to the metatable, but can I register "computed properties"?

For example, foo:bar would be equivalent to foo:get_bar() and foo:bar = 1234 equivalent to foo:set_bar(1234).

Thanks!

[vegorov-rbx]

__index and __newindex can be functions, so you can make the redirection to function calls there.

As a base, I would recommend looking at https://www.lua.org/pil/13.4.4.html and building upon that.

[natinusala]

This works great, thanks!

Now for the type checking part, is there a way to declare read-only properties using the declare syntax? Right now I have the following:

declare class Foo
    bar: number
end

Or do I have to abandon the declare syntax and manually craft the property definition in C++ to mark it as read-only?