How can I do "presets" in Django models -

i create store of products.

class product(models.model):     name = models.charfield(verbose_name=_(u'name'), max_length=200)     quantity = models.integerfield(verbose_name=_(u'quantity'))  >>> product.objects.create(name="egg", quantity="100") >>> product.objects.create(name="ham", quantity="10") 

now want create recipes, like: scrambled eggs 3 eggs , 1 piece of ham. tried describe like:

class recipe(models.model):     name = models.charfield(verbose_name=_(u'name'), max_length=200)     items = models.manytomanyfield('product', related_name='recipe_sets') 

but stuck in description number of required products 1 recipe.

should put quantity in other model? how can calculate number of servings (depending on quantity of product)? there elegant way or application deduction of products (as result of cooking 1 dish)?

you're going need table. manytomany create intermediate table linking 2 models have. if you're more explicit in how table created, can add fields onto linking table.

see documentation extra fields on many many relationships. basically, you'd have model:

class ingredients(models.model):     product = models.foreignkey(product)     recipe = models.foreignkey(recipe)     quantity = models.somefield(..) 

and change recipe definition manytomanyfield:

items = models.manytomanyfield('product', related_name='recipe_sets', through='ingredients')