EntityIndex

[sschmid]

An EntityIndex can speed up retrieving entities dramatically. Entities can be indexed similar to a index in a database.
Instead of iterating over all entities with a e.g. a position and checking if pos == (1, 2), an EntityIndex can observe group(Position) and index entities already. Getting all entities with pos == (1, 2) is constant speed of Dictionary access (=> very fast).

EntityIndex allows multiple entities with same key (key can be e.g. position or name)
PrimaryIndex ensures there is only one entity for a given key.

[sschmid]

A code generator is planned for a future version. See #75

public const string PositionKey = "Position":

public static void AddEntityIndices(Pool pool) {
    // Position index, key type is IntVector2
    var entityIndex = new EntityIndex<IntVector2>(
        pool.GetGroup(Matcher.Position),
        (entity, component) => { // How to create a key based on entity and component
            var positionComponent = component as PositionComponent;
            return positionComponent != null
                ? positionComponent.value
                : entity.position.value;
        });

    pool.AddEntityIndex(
        PositionKey, // Any unique name
        entityIndex
    );
}

public static HashSet<Entity> GetEntitiesWithPosition(this Pool pool, IntVector2 position) {
    var index = (EntityIndex<IntVector2>)pool.GetEntityIndex(PositionKey);
    return index.GetEntities(position);
}

var entities = pool.GetEntitiesWithPosition(pos); // fast index access

[echeg]

I try:

[Game]
public class CardComponent : IComponent
{
    public int Id;
    [IndexKey("CardT")]
    public TypeCard CardType; // want to integrate
    public Rarity CardRarity;
}

public class GameController : MonoBehaviour {
    void Start()
    {
       _pool = Pools.sharedInstance.game = Pools.CreateGamePool();
       AddEntityIndices(_pool);
   }

    public static void AddEntityIndices(Pool pool)
    {
        // Position index, key type is IntVector2
        var entityIndex = new EntityIndex<TypeCard>(
            pool.GetGroup(GameMatcher.Card), // Group to observe
            (entity, component) => ((CardComponent) component).CardType // How to create a key
            );

        // Add to pool by name
        pool.AddEntityIndex(
            GameComponentIds.Card.ToString(),
            entityIndex
        );
    }

And I get error on

(entity, component) => ((CardComponent) component).CardType // How to create a key

NullReferenceException: Object reference not set to an instance of an object
GameController.<AddEntityIndices>m__C (Entitas.Entity entity, IComponent component) (at Assets/Scripts/GameController.cs:45)

[sschmid]

I updated my previous comment. Try that

[echeg]

Thanks all works fine!

[echeg]

What you think about double indices?
Example:

public class CardComponent : IComponent
{
    public int Id;
    [IndexKey("CardTypeIndex")]
    public TypeCard CardType;
    [IndexKey("CardRarityIndex")]
    public Rarity CardRarity;
}

var entities = pool.GetEntitiesWithTypeAndRarity(TypeCard.solder, Rarity.Common);

Or indices from different components

Example

public class CardComponent : IComponent
{
    public int Id;
    [IndexKey("CardTypeIndex")]
    public TypeCard CardType;
    public Rarity CardRarity;
}
public class PlayerComponent : IComponent 
{
    [IndexKey("PlayerIndex")]
    public int Player;
}
var entities = pool.GetEntitiesWithTypeAndPlayer(TypeCard.solder, PlayerId);

[sschmid]

You can achieve sth like this already manually, but yeah, generating these things will be very handy