Symfony/ Twig: Filter-filter a collection - symfony

Question

Newbie here. Using Symfony 3.4.
I have a Collection of EntityType formtypes I created with the form builder. I'm trying to deposit them on the page selectively. I'd like to loop through them all several times on my template, spitting some of them out according to specific criteria (for instance, the value of a "HiddenType" subtype).
For instance, let's say I had a collection of Movies, some of which have a "Rating" HiddenType. My task is to spit them out selectively in several separate "Rating" sections (i.e. all the R-Rated movies in a single section).
Edit: But! Ratings are user-imputed; dynamically-generated elsewhere. So I can't just make a finite amount of "sections" ahead of time.
My first thought was
{% for rating in ratings %}
<h1>{{rating}}-Rated Movies</h1>
{% for movie in form.movies %}
{% if movie.rating = "R" %}
{{movie}} // put movie formtype/ collection member here somehow...?
{% endif %}
{% endfor %}
{% endfor %}
But I also read that twig has a "filter" filter:
{% for rating in ratings %}
<h1>{{rating}}-Rated Movies</h1>
{% for movie in movies|filter(m=> m.rating == rating) -%}
{{ m }} //put movie formtype/ collection member here somehow...?
{% endfor %}
{% endfor %}
Either way, though, I can't really reconcile the functions I'm familiar with for converting forms to actual html (e.g. form_row() ) with the either of these methods.
Any ideas?

Answer 1

You need to order the movies in your Form by rating. Then in your template do something like this:
{% set rating = null %}
{% for movieForm in form.movies %}
{% set movie = movieForm.vars.value %} <= check if this is the movie entity by dumping it
{% if movie.rating != rating %}
<h1>{{ movie.rating }}</strong>
{% set rating = movie.rating %}
{% endif %}
{{ form_row(movieForm) }}
{% endfor %}