Creating a Django Model Field in Python for Lists

I need to convert the Char field “device_id” into either a list field or an array field while ensuring that the current data in the field is retained. This will allow the field to accommodate multiple device ids. After making this change, the field should be removed, and migrations should be re-run.


Question:

In my models.py file, I have a Django model defined as follows:

class Inventory(models.Model):
    player = models.CharField(max_length=30)
    apples = models.IntegerField()
    bananas = models.IntegerField()

Is it possible to dynamically create field names from a list where each “player” has varying numbers of fruits in their inventory? Currently, the list includes “apples” and “bananas,” but in the future, I would like to include “apples,” “oranges,” and “lemons.


Solution:

Consider exploring the usage of models.ManyToManyField with a through-relationship. Relevant documentation can be found at the following links:
– https://docs.djangoproject.com/en/3.0/topics/db/examples/many_to_many/
– https://docs.djangoproject.com/en/3.0/ref/models/fields/#django.db.models.ManyToManyField.through

class Fruit(models.Model):
    name = models.CharField(max_length=30)
class Inventory(models.Model):
    player = models.CharField(max_length=30)
    fruits = models.ManyToManyField(
        Fruit,
        through='FruitContent'
    )
class FruitContent(models.Model):
    fruit = models.ForeignKey(Fruit, models.CASCADE)
    inventory = models.ForeignKey(Inventory, models.CASCADE)
    count = models.PositiveIntegerField()
    # Protect your data structure
    class Meta:
        constraints = [
            UniqueConstraint(fields=['fruit', 'inventory'], name='unique_ownership')
        ]

Maintaining your Inventory model is necessary, but the current approach feels somewhat clumsy. Personally, I would prefer an alternative method like this:

class Fruit(models.Model):
    name = models.CharField(max_length=30)
class Player(models.Model):
    name = models.CharField(max_length=30)
    inventory = models.ManyToManyField(
        Fruit,
        through='PlayerFruits'
    )
class PlayerFruits(models.Model):
    fruit = models.ForeignKey(Fruit, models.CASCADE)
    player = models.ForeignKey(Player, models.CASCADE)
    count = models.PositiveIntegerField()
    # Protect your data structure
    class Meta:
        constraints = [
            UniqueConstraint(fields=['fruit', 'player'], name='unique_ownership')

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