A little snippet showing how Lua could be used together with Specs.

specs-lua.rs

#[macro_use]
extern crate error_chain;
extern crate hlua;
extern crate specs;

use std::collections::HashMap;

error_chain! {
    errors {
        NoSuchComponent(name: String) {
            description("Requested component is not registered")
            display("Requested component {:?} is not registered", name)
        }
    }
}

struct LuaComponent {
    value: hlua::AnyLuaValue,
}

impl specs::Component for LuaComponent {
    type Storage = specs::DenseVecStorage<Self>;
}

fn main() {
    let mut component_map = HashMap::new(); // String -> id mapping with ids starting at 1
    let mut world = specs::World::new();

    {
        let mut lua = hlua::Lua::new();

        lua.set(
            "world_register",
            hlua::function1(|name: String| {
                let len = component_map.len();
                let id = len + 1;
                component_map.insert(name, id);
                world.register_with_id::<LuaComponent>(id);
            }),
        );

        lua.execute::<()>("world_register(\"MyComp\")").unwrap();
    }

    println!("Components: {:#?}", &component_map);
    assert_eq!(component_map.get("MyComp"), Some(&1));

    {
        let mut lua = hlua::Lua::new();

        lua.set(
            "read",
            hlua::function1::<_, Result<_>, _>(|s: String| {
                let &id: &usize = component_map
                    .get(&s)
                    .chain_err(|| ErrorKind::NoSuchComponent(s))?;
                let comp = world.read_with_id::<LuaComponent>(id);

                Ok(5) // TODO: implement `Push` for e.g. `LuaStorage`
            }),
        );
    }
}