mirror of
https://github.com/bevyengine/bevy
synced 2024-12-23 19:43:07 +00:00
7dcfaaef67
# Objective https://github.com/bevyengine/bevy/pull/4447 adds functions that can fetch resources/components as `*const ()` ptr by providing the `ComponentId`. This alone is not enough for them to be usable safely with reflection, because there is no general way to go from the raw pointer to a `&dyn Reflect` which is the pointer + a pointer to the VTable of the `Reflect` impl. By adding a `ReflectFromPtr` type that is included in the type type registration when deriving `Reflect`, safe functions can be implemented in scripting languages that don't assume a type layout and can access the component data via reflection: ```rust #[derive(Reflect)] struct StringResource { value: String } ``` ```lua local res_id = world:resource_id_by_name("example::StringResource") local res = world:resource(res_id) print(res.value) ``` ## Solution 1. add a `ReflectFromPtr` type with a `FromType<T: Reflect>` implementation and the following methods: - ` pub unsafe fn as_reflect_ptr<'a>(&self, val: Ptr<'a>) -> &'a dyn Reflect` - ` pub unsafe fn as_reflect_ptr_mut<'a>(&self, val: PtrMut<'a>) -> &'a mud dyn Reflect` Safety requirements of the methods are that you need to check that the `ReflectFromPtr` was constructed for the correct type. 2. add that type to the `TypeRegistration` in the `GetTypeRegistration` impl generated by `#[derive(Reflect)]`. This is different to other reflected traits because it doesn't need `#[reflect(ReflectReflectFromPtr)]` which IMO should be there by default. Co-authored-by: Jakob Hellermann <hellermann@sipgate.de> Co-authored-by: Carter Anderson <mcanders1@gmail.com> |
||
|---|---|---|
| .. | ||
| src | ||
| Cargo.toml | ||