Tracking

Shipyard comes with built-in tracking for insertion, modification, deletion and removal.

Declaration

Tracking is set with the Component trait. You can select individual operations or use All to track everything.

struct Life(f32);
impl Component for Life {
    type Tracking = track::Modification;
}

// or with the proc macro

#[derive(Component)]
#[track(Modification)]
struct Life(f32);

Usage

When inside a workload you will get information about operations that happened since the last time the current system ran.
Outside workloads you'll get information since the last call to clear_*.

Inserted or Modified

You can iterate inserted and modified components by calling inserted, modified or inserted_or_modified on a view before making the iterator. (*_mut versions also exist).

fn run(life: View<Life>, mut is_dead: ViewMut<IsDead>) {
    for (entity, life) in life.modified().iter().with_id() {
        if life.0 <= 0.0 {
            is_dead.add_component_unchecked(entity, IsDead);
        }
    }
}

Removed or Deleted

The difference between remove and delete can be understood from their signature:

fn delete(&mut self, entity: EntityId) -> bool {}
fn remove(&mut self, entity: EntityId) -> Option<T> {}

deletion stores the component whereas removal gives it back immediately.
Components can be deleted or removed but whole entities can only be deleted (at least for now).

Removed and deleted components cannot be accessed with iter but with removed, deleted or removed_or_deleted methods.

Reset

Inside workloads tracking information is automatically reset.
You will always get the operations that happened since the last run of the system.

You can reset tracking information outside of workload with:

• clear_all_inserted
• clear_all_modified
• clear_all_inserted_and_modified
• clear_all_removed
• clear_all_deleted
• clear_all_removed_and_deleted

You can also reset removed and deleted information older than some timestamp.

Use World::get_tracking_timestamp or AllStorages::get_tracking_timestamp to get a timestamp.
Then call clear_all_deleted_older_than_timestamp, clear_all_removed_older_than_timestamp or clear_all_removed_and_deleted_older_than_timestamp.