I'm trying to create a struct that will use mlua crate to generate some data.
Mlua interface is pretty simple - basically I need to make a central mlua::Lua struct that provides all the services.
So basically my struct could look like this:
pub struct DataGenerator {
lua: Lua,
}
impl DataGenerator {
pub fn give_me_some_data(&self) -> Vec<u64> {
let function: Function = lua.globals().get("my_function").unwrap(); // lookup the code to run
let result = function.call(...); // now run the code
// ... process the results
}
}
However, that's not very efficient, because I'm looking up the function each time (and yes, I profiled that and it adds non-negligible amount of time). It would be nice to cache the returned Function object.
The problem is, Function is tied to the lifetime of Lua, so actually it has a signature Function<'lua>.
And that's a bummer, a naive way of doing it doesn't work:
pub struct DataGenerator {
lua: Pin<Box<Lua>>,
main_f: Function<'static>
}
impl DataGenerator {
pub fn new() -> DataGenerator {
let lua = Pin::new(Box::new(Lua::new()));
lua.load("some lua code ...").exec().unwrap();
let main_f = lua.globals().get("my_function").unwrap();
DataGenerator { lua, main_f } // error: borrowed value does not live long enough
}
I think it should be doable, because the object under Pin should never move, and it definitely lives as long as the DataGenerator. What is the idiomatic way to do it?