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 of this crate is to efficiently store and access individual components without Boxing them.

The approach used in this crate 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::{EntityStorage, Archetype};

#[derive(Clone)]
struct Barks {
    bark_sound: String,
}

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

#[derive(Clone)]
struct Eats {
    favorite_food: String,
    eaten_food: Vec<String>,
}

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

#[derive(Clone)]
struct Animal {
    weight: f32,
    habitat: String,
}

#[derive(Clone, Archetype)]
struct Dog {
    animal: Animal,
    barks: Barks,
    eats: Eats,
}

#[derive(Clone, Archetype)]
struct Bird(Animal, Eats);

fn main() {
    let mut storage = EntityStorage::new();

    let super_dog = storage.add_entity(Dog {
        animal: Animal { weight: 30.0, habitat: "forest".to_string(), },
        barks: Barks { bark_sound: "bark.ogg".to_string(), },
        eats: Eats { favorite_food: "meat".to_string(), eaten_food: vec![] },
    });

    let hummingbird = storage.add_entity(Bird(
        Animal { weight: 5.0, habitat: "gardens".to_string() },
        Eats { favorite_food: "apples".to_string(), eaten_food: vec![] }
    ));

    let super_dog_barks = storage.get::<Barks>(&super_dog).unwrap();
    super_dog_barks.bark();

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

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