Derive Macro Resource 

#[derive(Resource)]
{
    // Attributes available to this derive:
    #[component]
    #[require]
}

Implement the Resource trait.

Immutability

#[derive(Resource)]
#[component(immutable)]
struct MyResource;

Hooks

#[derive(Resource)]
#[component(hook_name = function)]
struct MyResource;

where hook_name is on_add, on_insert, on_discard or on_remove; function can be either a path, e.g. some_function::<Self>, or a function call that returns a function that can be turned into a ComponentHook, e.g. get_closure("Hi!"). function can be elided if the path is Self::on_add, Self::on_insert etc.