Formset inside a ModelForm - django

Question

So lets try to explain:
I have a model called inventory, which serves to handle my products and their quantity. And I have another model that I would ask to do a certain service and would need to inform how many products and their quantity would be needed to complete that same service.
My problem is, I am using a ModelForm to render my form, but with this I just can select one product in the field items(that is a foreignkey of Inventory) and can't inform how many items would be needed. So, I'd like something to my user select one or more products from my inventory and inform how many them he will need to complete de service. I read about formset and seems to be what I need, but i can't figure out how to put in my code, or inside of my actually modelForm.
inventory models:
class Inventory(models.Model):
name= models.Charfield(max_lenght=100)
description = models.TextField()
quantity = models.PositiveIntegerField()
......
service models:
class Service(models.Model):
name = models.Charfield(max_length=100)
items = models.ForeignKey(Inventory, on_delete=models.DO_NOTHING)
description = models.TextField()
date= models.DateField(default=datetime.date.today)
....
views:
class CreateServiceView(CreateView):
model = Service
form_class = ServiceModelForm
template_name = 'service/create_service.html'
success_url = reverse_lazy('service:list_service')
template:
{% extends 'base.html' %}
{% load bootstrap4 %}
{% block content %}
<form method="post">
{%csrf_token %}
<table class="table">
{{ form }}
</table>
<tr>
<td>
<a href="service:list_service">
<button type="submit" class="btn btn-primary">Save</button>
</a>
<a href="#">
<button type="reset" class="btn btn-primary">Cancel</button>
</a>
</td>
</tr>
</form>
{% endblock %}
I need to change this field to something which I would select the item and put the quantity.

Answer 1

Based on how you named your variable items with a "s", I derive that you mean to use the same service for multiple inventories, right?
In that case you cannot use items = models.ForeignKey(Inventory, ...) in Service. Rather use service = models.ForeignKey(Service, ...) in Inventory.
This way every Inventory object is related to exactly one Service object. You can then access all the inventory-objects of a specific service by doing service.inventory_set.all()