I'm working on a API for a project and I have a relationship Order/Products through OrderProducts like this:
In models.py
class Product(models.Model):
...
class Order(models.Model):
products = models.ManyToManyField(Product, verbose_name='Products', through='OrderProducts')
...
class OrderProducts(models.Model):
order = models.ForeignKey(Order)
product = models.ForeignKey(Product)
...
Now, when I load an Order through the API I'd like to get the related Products as well, so I tried this (with django-tastypie):
In order/api.py
class OrderResource(ModelResource):
products = fields.ToManyField('order.api.ProductResource', products, full=True)
class Meta:
queryset = Order.objects.all()
resource_name = 'order'
Everything works for listing Order resources. I get order resources with product data embedded.
The problem is that I am not able to create or edit Order objects using the api. Since I am using a through model in ManytoMany relation, the ManyToManyField(products) does not have the .add() methods. But tastypie is trying to call .add() on the products field in OrderResource when posting/putting data to it.
{"error_message": "'ManyRelatedManager' object has no attribute 'add'", "traceback": "Traceback (most recent call last):\n\n File \"/Library/Python/2.7/site-packages/tastypie/resources.py\", line 192, in wrapper\n response = callback(request, *args, **kwargs)\n\n File \"/Library/Python/2.7/site-packages/tastypie/resources.py\", line 397, in dispatch_list\n return self.dispatch('list', request, **kwargs)\n\n File \"/Library/Python/2.7/site-packages/tastypie/resources.py\", line 427, in dispatch\n response = method(request, **kwargs)\n\n File \"/Library/Python/2.7/site-packages/tastypie/resources.py\", line 1165, in post_list\n updated_bundle = self.obj_create(bundle, request=request, **self.remove_api_resource_names(kwargs))\n\n File \"/Library/Python/2.7/site-packages/tastypie/resources.py\", line 1784, in obj_create\n self.save_m2m(m2m_bundle)\n\n File \"/Library/Python/2.7/site-packages/tastypie/resources.py\", line 1954, in save_m2m\n related_mngr.add(*related_objs)\n\nAttributeError: 'ManyRelatedManager' object has no attribute 'add'\n"}
Since you needed the manytomany field only for listing, a better solution is to add readonly=True
on OrderResource
's products
field. This removes the need of overriding save_m2m
method. For completeness:
class OrderResource(ModelResource):
products = fields.ToManyField('order.api.ProductResource', products,
readonly=True, full=True)
class Meta:
queryset = Order.objects.all()
resource_name = 'order'
The solution lies in overriding the save_m2m() method on the resource. In my case I needed the manytomany field for only listing, so overridden the save_m2m() method to do nothing.
If you are allowed to modify class OrderProducts
, adding auto_created = True
might solve your problem, i.e.,
class OrderProducts(models.Model):
class Meta:
auto_created = True
If you cannot change class OrderProducts
, try the following tastypie patch.
---------------------------- tastypie/resources.py ----------------------------
index 2cd869e..aadf874 100644
@@ -2383,7 +2383,20 @@ class BaseModelResource(Resource):
related_resource.save(updated_related_bundle)
related_objs.append(updated_related_bundle.obj)
- related_mngr.add(*related_objs)
+ if hasattr(related_mngr, 'through'):
+ through = getattr(related_mngr, 'through')
+ if not through._meta.auto_created:
+ for related_obj in related_objs:
+ args = dict()
+ args[related_mngr.source_field_name] = bundle.obj
+ args[related_mngr.target_field_name] = related_obj
+ through_obj = through(**args)
+ through_obj.save()
+ else:
+ related_mngr.add(*related_objs)
+ else:
+ related_mngr.add(*related_objs)
def detail_uri_kwargs(self, bundle_or_obj):
"""
In Django 1.7, the error message is changed to "Cannot set values on a ManyToManyField which specifies an intermediary model". The solution is the same.
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