```
class CatalogModel {
  static List<Item> items;
  static Item getById(int id) =>
      items.firstWhere((element) => element.id == id, orElse: null);
  static Item getByPosition(int pos) => items[pos];
}

```

I'm trying to create the class with a static list 'items', where I'm getting the following error:

> 
> The non-nullable variable 'items' must be initialized. Try adding an
> initializer expression.
> 
> 
> 

What should I do?