return table from registry.add_method

[brentp]

Hi, I am using register_user_type as below. I can see how to return a single Integer value when the user calls, e.g variant:info("key") but not how to return a lua table. How can I return a table in this case?

fn register_variant(lua: &Lua) -> mlua::Result<()> {

   lua.register_userdata_type::<Variant>(|reg| {
        reg.add_method("info", |_, this: &Variant, key: String| {
            let info = this.0.info(key.as_bytes());
            info.integer()
                .map(|v| {
                    //let mut t = lua.create_table().expect("error creating table");
                    match v {
                        Some(v) => {
                            // how to return lua table here rather than just the first value?
                            for val in v.iter() {
                                return Ok::<LuaValue<'_>, mlua::Error>(Value::Integer(*val));
                            }
                        }
                        None => return Ok(Value::Nil),
                    }
                    Ok(Value::Nil)
                })
                .map_err(|e| mlua::Error::ExternalError(Arc::new(e)))
        });
  }
}

thanks,
-Brent

[brentp]

bah, I see the first argument to the add_method function is Lua so I can use that.

[brentp]

is this an efficient (in terms of execution speed) way to provide read-only access to a vector of rust values (int this case, i32)?

        reg.add_method("info", |lua: &Lua, this: &Variant, key: String| {
            let info = this.0.info(key.as_bytes());
            info.integer()
                .map(|v| {
                    let t = lua.create_table().expect("error creating table");
                    match v {
                        Some(v) => {
                            // how to return lua table here rather than just the first value?
                            for (i, val) in v.iter().enumerate() {
                                t.raw_set(i + 1, *val).expect("error setting value");
                            }
                            Ok::<LuaValue<'_>, mlua::Error>(Value::Table(t))
                        }
                        None => Ok(Value::Nil),
                    }
                })
                .map_err(|e| mlua::Error::ExternalError(Arc::new(e)))
        });

[khvzak]

I would recommend createing a table with preallocated capacity to store N elements in array.
Also more efficient would be just using lua.create_sequence_from(v)

[brentp]

thank you!