gistfile1.swift

// Some global place
class CollisionMapping
{
    enum Layer : Uint32 {
        Terrain,
        Actors,
    }

    // Maps individual collision types (bird, pipe etc) to a smaller set of
    // more generic types to make them more manageable
    // Should be configured manually
    // Using strings instead of enums means it can be extended without modifying code
    map<string, Layer> colliderTypeToLayer;

    // Maps a Layer to a mask of layers to interact with
    // Should be configured manually
    UInt32 collidesWith[Layer.Size];
    UInt32 contactWith[Layer.Size];

    UInt32 getCollidesWithMask(string colliderType)
    {
        Layer layer = colliderTypeToLayer[derivedType];
        return collidesWith[layer];
    }

    UInt32 getContactWithMask(string colliderType)
    {
        Layer layer = colliderTypeToLayer[derviedType];
        return contactWith[layer];
    }
};


Bird.swift?

collisionName = "bird"

//In the Scene, will eventually make a factory out of this
self.bird.addComponent(Colliding(
    collisionsAs: ColliderType.Bird.rawValue,
    CollisionMapping.getCollidesWithMask(collisionName),
    CollisionMapping.getContactWithMask(collisionName)
)

self.bird.addComponent(
  Physical(dynamic:true,
           shape:.Circle(50)
  )
)