Crate bevy_entity_system

This crate provides easy to use way to make systems that operate on a single entity.

Warning

Currently there is a bug, individual entity systems don’t store their state. State is being shared across all entities that are being iterated by the system that resulted from into_system call. That means that Local, EntityReader and other SystemParam’s, that rely on it’s state property to be preserved between system runs, won’t work correctly. It is a huge footgun, so the work on fixing it is being done.

After fix, the API will change, user would need to explicitly specify the entities this system is allowed to run on. That means, you most probably would need to be able to mutate systems at runtime - something that bevy currently doesn’t support. I also work on a crate that will be able to provide you with such functionality - it is not published yet.

Example

#[derive(Component)]
struct Count(i32);
 
#[derive(Component)]
struct MyMarkerComponent;

fn my_entity_system(
    mut data: Data<&mut Count, With<MyMarkerComponent>>,
    mut commands: Commands
) {
    data.item.0 += 1;
    commands.spawn(Count(10));
}

fn my_entity_system_with_input(input: In<i32>, mut data: Data<&mut Count>) {
    data.item.0 += *input;
}

bevy_ecs::system::assert_is_system(my_entity_system.into_system());
bevy_ecs::system::assert_is_system(my_entity_system_with_input.into_system());

Modules

data_match

Contains DataMatch

implementors

Built in implementations of EntitySystem

into_entity_system

Convenience in working with EntitySystems

into_system

Implementation of IntoSystem

marked_entity_system

Contains functionality to run EntitySystems that should be marked in order to implement this trait This is necessary to avoid conflicting implementations when implementing trait for rust functions

prelude

Prelude module

Traits

EntitySystem

Trait implemented for all functions that can be used as Systems and operate on a single Entity. Such system can only be run for entities that match it’s Data and Filter

ReadOnlyEntitySystem

Implemented for EntitySystems that only read data from the world