Displaying related data from two or more tables in a DetailView

Question

I did not find information on how all named arguments **kwargs are passed in the overridden "get_context_data" method in the view call.

There are 3 models:

class User(models.Model):
    email = models.CharField(unique=True)
    company_id = models.IntegerField(blank=True, null=True)
    first_name = models.CharField(blank=True, null=True)
    last_name = models.CharField(blank=True, null=True)

class Company(models.Model):
    logo = models.CharField(blank=True, null=True)
    name = models.CharField(blank=True, null=True)
    full_name = models.CharField(blank=True, null=True)
    address = models.CharField(blank=True, null=True)
    phone = models.CharField(blank=True, null=True)
    email = models.CharField(blank=True, null=True)
    kpp = models.CharField(blank=True, null=True)
    okved = models.CharField(blank=True, null=True)
    bik = models.CharField(blank=True, null=True)   

class Order(models.Model):
    user_id = models.IntegerField(blank=True, null=True)
    amount_total_cents = models.BigIntegerField()
    amount_mean_cents = models.BigIntegerField()
    created_at = models.DateTimeField()

Communication between models:

Company-User 1 to M, User-Order 1 to M

There are no problems with direct output of data in the view without overriding the "get_context_data" method. However, there are no problems when overriding the method and linking two tables through the primary key:

1. company/urls.py

urlpatterns = [
    path('company/<int:pk>', CompanyShow.as_view(), name='company_show')
]

company/views.py

class CompanyShow(DetailView):
    model = Company
    template_name = 'company/company_show.html'
    context_object_name = 'company'

    def get_context_data(self, **kwargs):
        context = super(CompanyShow, self).get_context_data(**kwargs)
        context['users'] = User.objects.filter(company_id = self.kwargs['pk'])
        return context

company_show.html

    <p>ID: {{ company.id }}</p>
    <p>Name: {{ company.name }}</p>
    <p>Members:
    {% for user in users %}
        <li>
        <a href="{% url 'user:user_show' user.id %}">{{ user }}</a>
        </li>
    {% endfor %}
    </p>

2. user/urls.py

urlpatterns = [
    path('user/<int:pk>', UserShow.as_view(), name='user_show')
]

user/views.py

class UserShow(DetailView):
    model = User
    template_name = 'user/user_show.html'
    context_object_name = 'user'

user_show.html

    <p>ID: {{ user.id}}</p>
    <p>Name: {{ user.first_name }}</p>
    <p>Surname: {{ user.last_name }}</p>
    {% if user.company_id %}
        <a href="{% url 'company:company_show' user.company_id %}">
            Company profile (id {{ user.company_id }})
        </a>
    {% else %}
        No company
    {% endif %}

The question is the following:

What matching parameter should be passed from **kwargs to order/views.py so that the list of required objects is filtered according to the "user" table "id" in the "order" table of the "user_id" field? And according to the result, it is required to display the company in .html - how to connect the table of "users" and the "company" next?

However, the difficulty is when the binding goes in orders:

order/urls.py

urlpatterns = [
    path('order/<int:pk>', OrderShow.as_view(), name='order_show')
]

order/views.py

class OrderShow(DetailView):
    model = Order
    template_name = 'order/order_show.html'
    context_object_name = 'order'

    def get_context_data(self, **kwargs):
        context = super(OrderShow, self).get_context_data(**kwargs)
        context['users'] = User.objects.filter(id = self.kwargs['user_id'])  
        return context

order_show.html

    <p> Member:
    {% for user in users %}
        <li>
        <a href="{% url 'user:user_show' user.id %}">{{ user }}</a>
        </li>
    {% endfor %}
    </p>

In the described implementation, the error:

Exception Type:     KeyError
Exception Value:    'user_id'

Answer 1

It turns out to be a simple solution, if not attached to **kwargs: context['users'] = User.objects.filter(id = self.object.user_id)

Final view:

class OrderShow(DetailView):
    model = Order
    template_name = 'order/order_show.html'
    context_object_name = 'order'
    
    def get_context_data(self, **kwargs):
        context = super(OrderShow, self).get_context_data(**kwargs)   
        context['users'] = User.objects.filter(id = self.object.user_id)  
        return context

And with 3 tables, where two do not have a direct relationship:

class OrderShow(DetailView):
    model = Order
    template_name = 'order/order_show.html'
    context_object_name = 'order'
    
    def get_context_data(self, **kwargs):
        context = super(OrderShow, self).get_context_data(**kwargs)   
        context['users'] = User.objects.filter(id = self.object.user_id)        
        for user in context['users']:
            context['companies'] = Company.objects.filter(id=user.company_id)
        return context