impl<'a> PrefabBuiler<'a>{ 
  pub fn new(world: &'a mut World)->PrefabBuiler<'a>{
    PrefabBuiler{
      world
    }
  }

  pub fn create(&mut self, prefab: Vec<Components>) -> Entity{
    let mut builder = self.world.create_entity();
    for component in prefab {
      builder = builder.with(component);
    }    
    builder.build()
  }
}

pub fn PlayerPrefab () -> Vec<Components> {
  vec![
    Components::Position(Position{
      x: 0.0,
      y: 0.0
    })
  ]
}

let mut builder = PrefabBuiler::new(&mut world);
    builder.create(PlayerPrefab());