Similarly, if you're using the :doc:`collection</reference/forms/types/collection>`

form type where your underlying collection data is an object (like with Doctrine's

``ArrayCollection``), then ``by_reference`` must be set to ``false`` if you

need thesetter(e.g. ``setAuthors()``) to be called.

need theadder and remover(e.g. ``addAuthor()`` and ``removeAuthor()``) to be called.