Attribute Macro resource_impl 

#[resource_impl]

Helper attribute for Resource implementations

When an impl Resource for Type block is annotated with this attribute, it will automatically set the IMPLEMENTS_... associated constants for all implemented callback methods. Thus, instead of

struct ResourceType {}

impl Resource for ResourceType
{
    const IMPLEMENTS_DESTRUCTOR: bool = true;

    fn destructor(...) { ... }
}

it is enough to provide the implementation:

#[rustler::resource_impl]
impl Resource for ResourceType
{
    fn destructor(...) { ... }
}

The resource type is also automatically registered by default, it does not have to be manually registered in a load callback. The automatic registration can be disabled with the register parameter:

#[rustler::resource_impl]
impl Resource for ResourceType
{
    ...
}

// no load callback necessary

If registration is disabled, the resource type has to be registered manually. It is not possible to use the old resource! macro for this, as that injects another impl Resource block.

#[rustler::resource_impl(register = false)]
impl Resource for ResourceType
{
    ...
}

pub fn on_load(env: Env) -> bool {
    env.register::<ResourceType>().is_ok()
}