Sub Categorized Status Choices in Django - django

Question

Let's say I have a model of sandwiches, and I want to say what protein you want to put on the sandwich:
class Sandwich(models.Model):
protein_choices = (
('n', 'Please Choose'),
('e1', 'Eggplant'),
('e2', 'Hummus'),
('v1', 'Provolone'),
('v2', 'Egg'),
('p1', 'Fish'),
('c1', 'Beef'),
('c2', 'Chicken'),
('c3', 'Pork'),
)
protein = models.CharField(
max_length=2,
choices=protein_choices,
default='n',
)
How could I make the choices categorized by vEgan, Vegetarian, Pescatarian, or Carnivore?
I want to be able to check its category (is the sandwich Vegan[assuming categorizations don't overlap]?), and I have been using a model.Manager, but I want to ensure that all choices have a single category (I think this is the missing link, and don't think testing is the right way) and only one choice is selected (which is already handled by the status structure presented).
Should this be handled in a model.Form, a 1->M relationship with some other structure, or through model.Managers and something else?

Answer 1

Another option is an in-memory data structure and interface that maps your status keys to their appropriate category. For example you could use an Enum with a category property as the basis for your Choices. If the relationships between those strings ends up being something you want to manage in the database you can always refactor and add a migration.
As you've noted building a tree structure in your models as others have suggested makes for a lot of joins.. and in that case it might be useful to take a look at django-treebeard or django-categories and check if it's reasonable to take on that additional dependency.

Answer 2

I think having separate models for protein and category will be good.
Example:
class Protein(models.Model):
name = models.CharField(max_length=20)
class ProteinCategory(models.Model):
protein = models.ForeignKey(to="Protein")
name = models.CharField(max_length=20)
class Sandwich(models.Model):
protein = models.ForeignKey(to="Protein")
Use ManyToManyField instead of ForeignKey in Sandwich model, if a Sandwich contains many Protein.
Use OneToOneField in ProteinCategory model, if a Protein can be in one and only one ProteinCategory.

Answer 3

I suggest using different models for this task.
Continuing with your example, you could have the proteins, which each belong to a single category (as per your request in the comments to your question):
class ProteinCategory(models.Model):
name = models.CharField(max_length=20)
class Protein(models.Model):
name = models.CharField(max_length=20)
category = models.ForeignKey(to=ProteinCategory)
Then you could assign a single protein (as per your request) for each sandwich:
class Sandwich(models.Model):
name = models.CharField(max_length=20)
protein = models.ForeignKey(to=Protein)
Does this seem to solve your issue?