Embedding a collection of forms Symfony2 forms with adding and deleting allowed

Question

In Symfony2, if I embed a collection of forms pointing at a many to one relationship in Doctrine and allow adding and deletion, if I delete a record from the beginning, add one

Answer 1

Based on the Akkumulator's answer and comment and some experimentation, I did this:

Create new fields (using Javascript as described in the documentation) with __name__ replaced not by a number but by a string: new_ followed by an forever increasing number that has nothing to do with the list (e.g. new_1, new_2, new_3...)

I don't have to push the primary keys into the forms and I don't need indexBy either - that's good, because indexBy felt like it was too far removed from the form, ending in having the Action at a distance anti-pattern.

Why this works:

• PHP arrays aren't like those in other languages. They're always dictionaries, so you can add string keys to them even if they only have numeric keys to start with.
• Because the Symfony collection is mapped by field name, new fields will not match existing data and deleted fields will not be matched to existing data (and thus be removed from the set)