Attribute Macro reflect_trait

#[reflect_trait]

A macro that automatically generates type data for traits, which their implementors can then register.

The output of this macro is a struct that takes reflected instances of the implementor’s type and returns the value as a trait object. Because of this, it can only be used on object-safe traits.

For a trait named MyTrait, this will generate the struct ReflectMyTrait. The generated struct can be created using FromType with any type that implements the trait. The creation and registration of this generated struct as type data can be automatically handled by #[derive(Reflect)].

Example

#[reflect_trait] // Generates `ReflectMyTrait`
trait MyTrait {
  fn print(&self) -> &str;
}

#[derive(Reflect)]
#[reflect(MyTrait)] // Automatically registers `ReflectMyTrait`
struct SomeStruct;

impl MyTrait for SomeStruct {
  fn print(&self) -> &str {
    "Hello, World!"
  }
}

// We can create the type data manually if we wanted:
let my_trait: ReflectMyTrait = FromType::<SomeStruct>::from_type();

// Or we can simply get it from the registry:
let mut registry = TypeRegistry::default();
registry.register::<SomeStruct>();
let my_trait = registry
  .get_type_data::<ReflectMyTrait>(TypeId::of::<SomeStruct>())
  .unwrap();

// Then use it on reflected data
let reflected: Box<dyn Reflect> = Box::new(SomeStruct);
let reflected_my_trait: &dyn MyTrait = my_trait.get(&*reflected).unwrap();
assert_eq!("Hello, World!", reflected_my_trait.print());