Hi!
As part of a crazy loosely typed system I have a function that returns a Box<Any +'static> that I can cast to a type I know it is. Unfortunately when I try and do that cast I get this exception:
src/components/mod.rs:35:69: 35:83 error: the trait `core::marker::Reflect` is not implemented for the type `T` [E0277]
src/components/mod.rs:35 let component_list : &'static SharedMutex<T> = *component_list_any.downcast_ref().expect("Invalid type for components list");
^~~~~~~~~~~~~~
Seems like an easy fix, add Reflect to the type constraint of the Any, but that yields this exception:
src/components/mod.rs:12:5: 12:25 error: use of unstable library feature 'reflect_marker': requires RFC and more experience (see issue #27749)
src/components/mod.rs:12 use std::marker::Reflect;
^~~~~~~~~~~~~~~~~~~~
That issue #27749 looks like it won't soon be solved, some new system that isn't done yet will first be implemented after which it is a bit unclear for me.
So that leaves me with the question: is there a workaround for this?
Alternatively, maybe I could redesign my system a bit, it's totally in an exploratory fase, so I'm very much open to suggestions. I have included the full source of the file my problem is in, the problem function is called get_components_lock.
/// Components are types that associate an entity with a set of properties
/// for each type a list of all its instances is kept so they can be iterated
/// over efficiently by systems.
///
/// Whenever a new component is created it is added to a list.
///
/// component! { physics, body: physics.RigidBody, physics_id: physics.ID }
///
use std::collections::{ HashSet, HashMap };
use std::any::{ Any, TypeId };
use shared_mutex::{ SharedMutex, SharedMutexReadGuard, SharedMutexWriteGuard };
pub mod example;
#[derive(Clone)]
pub struct Component {
pub name: TypeId,
pub get_component_list: fn () -> Box<Any + 'static>
}
lazy_static! {
pub static ref COMPONENTS: SharedMutex<HashMap<TypeId, Component>> = SharedMutex::new(HashMap::new());
}
pub fn register(component : Component) {
let mut components = COMPONENTS.write().expect("COMPONENTS lock corrupted");
components.insert(component.name, component);
}
pub fn get_components_lock<'mutex, T>(id : TypeId) -> SharedMutexReadGuard<'mutex, T> where T : 'static {
let components = COMPONENTS.read().expect("COMPONENTS lock corrupted");
let component = components.get(&id).expect("Unknown component type requested");
let component_list_any = (component.get_component_list)();
let component_list : &'static SharedMutex<T> = *component_list_any.downcast_ref().expect("Invalid type for components list");
return component_list.read().expect("Component LIST lock corrupted");
}
