#14113: Access to extra fields in M2M relations
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Reporter: jprafael | Owner: nobody
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: 1.2
Keywords: Many2ManyField intermediary fields | Stage: Unreviewed
Has_patch: 0 |
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I'm using a model similar to
{{{
#!python
class Recipe(models.Model):
name = models.CharField(max_length = 32, unique=True)
products = models.ManyToManyField(Product,
through="RecipeProduct")
class Product(models.Model):
name = models.CharField(max_length = 32, unique=True)
amound = models.IntegerField() # in stock
class RecipeProduct(models.Model):
recipe = models.ForeignKey(Recipe)
product = models.ForeignKey(Product)
amount = models.IntegerField()
}}}
And need to list all my recipes, along with their products' amounts.
{{{
#!python
Recipe.objects.select_related().all()
}}}
Gives access to the list of products in each recipe, but not access to the
amount field in the intermediary table.
Perhaps recipe.products.all() should merge the extra fields into the
Product objects by means of another parameter in the ManyToManyField
definition where the user can choose the fields to select (and the names
they would be accessible by) like:
{{{
#!python
products = models.ManyToManyField(Product, through="RecipeProduct",
extra_fields={'amount': 'recipe_amount'})
}}}
This would allow direct usage like:
{{{
#!python
{% for recipe in recipes %}
{% for product in recipe.products.all() %}
product: {{ product.name }} ({{ product.amount }} in
stock)
amount: {{ product.recipe_amound }}
{% endfor}
{% endfor %}
}}}
while avoiding name colision problems
--
Ticket URL: <http://code.djangoproject.com/ticket/14113>
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