How to make a manytomany connection correctly?

Question

Django

Good day. There are a couple of models, for example, describing a pizza recipe. Each pizza contains several ingredients. For each of the pizzas, the amount of a certain ingredient may be different, for example, on pizza 1 we add 100 grams of the pepper ingredient, and on pizza 2, only 50 grams of the same pepper ingredient. How to do it in models?

class Ingridient(models.Model):
    ingridient_name = models.CharField(u'Название ингридиента', max_length=255)
    
class Pizza(models.Model):
    pizza_name = models.CharField(u'Название пиццы', max_length=255)
    ingridients = models.ManyToManyField(Ingridient)

Answer 1

Because An M2M field is sugar in jang, it may not be obvious that in the database it is represented by two fields with a unique index on both fields. FK for one model and FK for another model. Additional fields cannot be specified in M2M, so you need to do something like this:

class Ingredient(models.Model):
    name = models.CharField(u'Название ингр_е_диента', max_length=255)
    
class Pizza(models.Model):
    name = models.CharField(u'Название пиццы', max_length=255)
    ingredients = models.ManyToManyField(Ingredient, through='PizzaIngredient')

class PizzaIngredient(models.Model):
    pizza = models.ForeignKey(Pizza)
    ingredient = models.ForeignKey(Ingredient)
    quantity = models.DecimalField(max_digits=9, decimal_places=2)
    unit = models.CharField(max_length=30)  # Единица измерения (граммы, ложки). Можно выделить в отдельную таблицу, если надо

    class Meta:
        unique_together = (('pizza', 'ingredient'),)

Answer 2

djbook.ru/rel1.8/topics/db/models.html#intermediar...
through who did you come up with?

Answer 3

For example, add a Recipe model

class Recipe(models.Model):
    ingridient = models.ForeignKey(Ingridient)
    quantity = models.DecimalField(...)

Then Pizza

class Pizza(models.Model):
    pizza_name = models.CharField(u'Название пиццы', max_length=255)
    component = models.ManyToManyField(Recipe)