Question

I have such model now: receipt contains components. component contain product.

The difference between component and product is, that component has quantity and measure unit:
eg. component is 100g sugar – sugar is a product.

So I need to make lots of components to satisfy different recipes – 100g sugar is not equal 200g sugar

I wonder if I can remodel it to kick off components – in pure sql it’s rather easy, but I’m trying to USE django – not making workarounds.

class Receipt(models.Model):
  name = models.CharField(max_length=128)
  (...)
  components = models.ManyToManyField(Component)

class Component(models.Model):
  quantity = models.FloatField(max_length=9)
  unit = models.ForeignKey(Unit)
  product = models.ForeignKey(Product)

class Product(models.Model):
  name = models.CharField(max_length = 128)

TIA

Answer 1

You can get rid of the Component model if you use a ManyToMany relationship using “through” in your Receipt model:
http://docs.djangoproject.com/en/1.2/topics/db/models/#intermediary-manytomany