With attribute

[marcoseiza]

Summary

Adds a new attribute to the LdtkEntity derive macro named with. It allows for bundles to implement custom initializers using a method. This macro takes in a scoped function with signature (e: EntityInstance) -> T where T is the field type.

Example

pub struct Bundle {
   #[with(foo_initializer)]
    foo: i32;
}

fn foo_initializer(_e: EntityInstance) -> i32 {
    4
}

Longer Example

#[derive(Clone, Default, Bundle)]
pub struct ColliderBundle {
    pub collider: Collider,
    pub rigid_body: RigidBody,
    pub damping: Damping,
    ...
}

#[derive(Bundle, Default, LdtkEntity)]
pub struct PlayerBundle {
    player: Player,
    #[with(player_collider)]
    #[bundle]
    collider: ColliderBundle,
}

fn player_collider(_: EntityInstance) -> ColliderBundle {
    ColliderBundle {
        collider: Collider::capsule(Vec2::new(0., -4.), Vec2::new(0., -12.), 5.),
        rigid_body: RigidBody::Dynamic,
        rotation_constraints: LockedAxes::ROTATION_LOCKED,
        damping: Damping {
            linear_damping: 10.0,
            ..Default::default()
        },
        ..Default::default()
    }
}

Issue

The same functionality can be done using from_entity_instance by filtering the identifier to the correct type. However, this could cause function bloat when many entities with different identifiers implement the same bundle. You can have cleaner and safer code separation with this with(function) attribute.

ToDo

• Ensure type safety of function return; the error messages aren't very good if the function doesn't return the correct type

[Trouv]

Thanks for the contribution. This is a great idea, and in hindsight it seems so obvious. Def wanna get this in.

[Trouv]

Please add some documentation w/ an example to src/app/ldtk_entity.rs

[marcoseiza]

Ready for another review!

[marcoseiza]

Checked with cargo test and cargo build, all pass!

[marcoseiza]

okay, third times the charm 😅

[marcoseiza]

Thanks @Trouv for reviewing!!