How to filter form options by foreign key? - Django Admin

Question

I need to show only objects that have the same foreign key company in Django in the admin view. What I got was to show only the related objects using get_queryset, but in the form fields appear all records.

My code:

models.py

class Company(models.Model):
    name = models.CharField(max_length=64)
    cnpj = models.CharField(max_length=14)
    active = models.BooleanField(default=False)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(null=True, blank=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name_plural = "Companies"


class User(models.Model):
    user = models.OneToOneField(BaseUser, on_delete=models.CASCADE)
    company = models.ForeignKey(Company, on_delete=models.CASCADE)
    department = models.ForeignKey(Department, on_delete=models.CASCADE)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(null=True, blank=True)

    def __str__(self):
        return f"{self.user.first_name} {self.user.last_name}"


class Category(models.Model):
    name = models.CharField(max_length=32)
    company = models.ForeignKey(Company, on_delete=models.CASCADE)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(null=True, blank=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name_plural = "Categories"

class Resource(models.Model):
    name = models.CharField(max_length=64)
    model = models.CharField(max_length=64)
    location = models.CharField(max_length=64)
    manufacturer = models.CharField(max_length=64)
    provider = models.CharField(max_length=64)
    serial = models.CharField(max_length=32)
    user = models.ForeignKey(
        User, null=True, blank=True, on_delete=models.CASCADE)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    company = models.ForeignKey(Company, on_delete=models.CASCADE)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(null=True, blank=True)

    def __str__(self):
        return self.name

admin.py

@admin.register(Resource)
class ResourceAdmin(admin.ModelAdmin):
    list_display = (
        'name',
        'model',
        'location',
        'manufacturer',
        'provider',
        'serial',
        'user', # Campo que precisa ser filtrado pela chave estrangeira de company
        'category', # Campo que precisa ser filtrado pela chave estrangeira de company
        'created_at'
    )

    def get_queryset(self, request):
        user = User.objects.get(user=request.user)
        return Resource.objects.filter(company=user.company)

Answer 1

Use two underscores to reference the foreign key (more on the subject here):

def get_queryset(self, request):
    return Resource.objects.filter(user__company=request.user.company)