Get variable name from meta object

[sybalos]

Hi!

I'm looking at the reflection system test code and documentation. Is there a way to iterate over an object member variable and get all the variable name (as string) ? I did figure out how to do it with values but not with names. Trough the registered hashed_string maybe ?

[Green-Sky]

I think you are supposed to use the Properties for that.
https://github.com/skypjack/entt/wiki/Crash-Course:-runtime-reflection-system#properties-and-meta-objects
and I am afraid, that you have to name them yourself. I use the dreaded macros for that.

[skypjack]

Iterate over meta data members is quite easy actually:

for(auto data: type.data()) {
    // ...
}

As for the variable names, EnTT doesn't attach this kind of information by default. However, you can use a property for that as suggested by @Green-Sky since they're literally meant for that. 👍

[mathisloge]

@skypjack I'm currently a bit lost about this.
My use case would be to get all type names, and channel them through to an inspector app. So you could inspect each type and see the name: value and make adjustments if the value is readable.

Currently I have a converter function which maps each type the the protocol version. However I would really like to just depend on the registered types and use the meta_any::type().is_* functions to determine the serialization.

Given the following code, what would be the most entt way of doing such things, since I would need to save each attribute of the type. Would it be "good" to use the custom or function field which returns a vector with all the names of methods, functions etc.?

struct TestRect
{
    int x;
    int y;
    int width;
    int height;
};
 entt::meta_factory<TestRect>(context)
        .type("TestRect"_hs)
        .data<&TestRect::x>("x"_hs)
        .data<&TestRect::y>("y"_hs)
        .data<&TestRect::width>("width"_hs)
        .data<&TestRect::height>("height"_hs);
   
entt::meta_any data_type = TestRect{};
    for(auto&& data : data_type.type().data()) {
        entt::meta_any x = data.second.get(data_type);
        std::println("Value {}={}", <<get_name_here>>, x);
    }
}

[Innokentiy-Alaytsev]

If nothing has drastically changed in the past years, the answer is the same: attach to every meta-item, including type itself (I believe it's possible), a property that holds it's name.

[mathisloge]

But that's the part I'm not quite get, the wiki doesn't really mention how to attach a property to a data member.

[Innokentiy-Alaytsev]

Apparently, it did change in the past years. If I understand correctly, now you have not properties, but traits and custom data.

[skypjack]

Yeah, there are no properties anymore. You can have them if you like by setting a map as custom data, ofc.
However, I suggest using an app specific custom data structure where you set the data of interest for you, rather than a generic map.
This test file and this part of the doc is where you want to start from probably.