Symfony 2: Building a form with related entities

Question

symfony

Example: There are three related entities: posts, comments, replies to comments.
Approximate connection: Post[comments] -> Comment[answers] -> Answer
Question: How to make a form in which you can edit / add comments and answers to them?

Answer 1

Clarification: I need a hint on how to use Form\Type (FormBuilderInterface, AbstractType) to make a connection between these three entities so that the template can use loop and form_row to display the edit elements of the data described above.

Answer 2

What's the catch?
Show how you are trying to do now?