entity_data

A container for entity component data.

An entity is an opaque identifier for an object. Each entity can have multiple components associated with it. Storage is based on ECS technique, but the main purpose is to efficiently store and access individual components without Boxing them.

The approach used in this library is superior to Rust's dynamic dispatch because components can have their separate fields and components of the same type are stored in a contiguous vector.

Example

use entity_data::EntityStorageLayout;
use entity_data::EntityStorage;

struct Barks {
    bark_sound: String,
}

impl Barks {
    fn bark(&self) {
        println!("{}", self.bark_sound);
    }
}

struct Eats {
    eaten_food: Vec<String>,
}

impl Eats {
    fn eat(&mut self, food: String) {
        self.eaten_food.push(food);
    }
}

struct Dog {
    favorite_food: String,
}

struct Bird {
    weight: f32,
    habitat: String,
}

fn main() {
    let mut layout = EntityStorageLayout::new();
    let type_dog = layout.add_archetype().with::<Dog>().with::<Barks>().with::<Eats>().build();
    let type_bird = layout.add_archetype().with::<Bird>().with::<Eats>().build();

    let mut storage = EntityStorage::new(&layout);

    let super_dog = storage.add_entity(type_dog)
        .with(Dog { favorite_food: "meat".to_string(), })
        .with(Eats { eaten_food: vec![] })
        .with(Barks { bark_sound: "bark.ogg".to_string() })
        .build();

    let hummingbird = storage.add_entity(type_bird)
        .with(Bird { weight: 0.07, habitat: "gardens".to_string() })
        .with(Eats { eaten_food: vec![] })
        .build();
    
    let super_dog_barks = storage.get::<Barks>(&super_dog).unwrap();
    super_dog_barks.bark();

    let super_dog_props = storage.get_mut::<Dog>(&super_dog).unwrap();
    super_dog_props.favorite_food = "beans".to_string();

    let hummingbird_eats = storage.get_mut::<Eats>(&hummingbird).unwrap();
    hummingbird_eats.eat("seeds".to_string());
}