Using `with_scope` in Locomotive CMS - locomotivecms

Question

###I have a question regarding the use of with_scope in Locomotive CMS.
To start I have a model, movies, with full fields, one of which is called film_etats with type: belongs_to.
I have another model, film_etats, where I have an etat field which is of type: string and another field movies with type: has_many.
This works okay - I get to see my data - but what I would like to do is to filter the information.
In the Locomotive CMS docs I find this:
https://doc.locomotivecms.com/docs/tags#with_scope
Here the first example.
{% with_scope author: 'John Doe' %}
{% for post in content_type.posts %}
{{ post.title }}
{% endfor %}
{% endwith_scope %}
So I did this:
{% with_scope film_etats.etat: 'Production' %}
{% for film in contents.film %}
etat du film : {{film.film_etats.etat}}
{% endfor %}
{% endwith_scope %}
but it does not work and what I want but a type error: undefined method `entries' for nil: NilClass
my model films
title_film => type (string)
film_etats => type belongs_to
my model film_etats
etat => type(string)
films => type(has_many)
thanks

Answer 1

First of all, your code is a little strange, because if it worked, all it would do is print out a list of the word "Production" many times. i.e.
etat du film : Production
etat du film : Production
etat du film : Production
....
The reason it's not working is that you can't use with_scope to filter based on a related model's field. The following code will print the title of all films in production.
{% with_scope etat: 'Production' %}
{% assign production = contents.film_etats.first %}
{% endwith_scope %}
Production Films:<br />
{% for film in production.films %}
- {{ film.title_film }}<br />
{% endfor %}