how to use backward relation in django tastypie - django

Question

this is my model
class Nisit(models.Model):
and this
class Page(models.Model):
followingNisit = models.ManyToManyField(Nisit,blank=True)
this is my resource
class NisitResource(ModelResource):
page = fields.ToManyField('chula.api.PageResource','page_set',null=True)
class Meta:
queryset = Nisit.objects.all()
resource_name = 'nisit'
filtering = {
'page' : ALL_WITH_RELATIONS,
'id' : ALL,
}
class PageResource(ModelResource):
followingNisit = fields.ToManyField(NisitResource, 'followingNisit',null=True)
reporter = fields.ManyToManyField(ReporterResource,'reporter')
followers_count = fields.CharField(attribute='followers_count')
class Meta:
queryset = Page.objects.all()
resource_name = 'page'
authorization= Authorization()
filtering = {
'id':ALL,
'followingNisit': ALL_WITH_RELATIONS,
}
It's ok when I request -------127.0.0.1:8000/api/v2/page/?format=json&followingNisit__id=1
But In the opposite way ,when i request ---------127.0.0.1:8000/api/v2/nisit/?format=json&page__id=1, I will get this error
{"error_message": "Cannot resolve keyword 'page_set' into field. Choices are: displayName, facebook, faculty, friend, id, major, n_id, name, page, password, picture, reporter, year_in_school", "traceback": "Traceback (most recent call last):\n\n File \"D:\\Study\\SeniorProject\\Code\\mysite\\tastypie\\resources.py\", line 202, in wrapper\n response = callback(request, *args, **kwargs)\n\n File \"D:\\Study\\SeniorProject\\Code\\mysite\\tastypie\\resources.py\", line 441, in dispatch_list\n return self.dispatch('list', request, **kwargs)\n\n File \"D:\\Study\\SeniorProject\\Code\\mysite\\tastypie\\resources.py\", line 474, in dispatch\n response = method(request, **kwargs)\n\n File \"D:\\Study\\SeniorProject\\Code\\mysite\\tastypie\\resources.py\", line 1127, in get_list\n objects = self.obj_get_list(request=request, **self.remove_api_resource_names(kwargs))\n\n File \"D:\\Study\\SeniorProject\\Code\\mysite\\tastypie\\resources.py\", line 1890, in obj_get_list\n base_object_list = self.apply_filters(request, applicable_filters)\n\n File \"D:\\Study\\SeniorProject\\Code\\mysite\\tastypie\\resources.py\", line 1862, in apply_filters\n return self.get_object_list(request).filter(**applicable_filters)\n\n File \"C:\\Python27\\lib\\site-packages\\django\\db\\models\\query.py\", line 624, in filter\n return self._filter_or_exclude(False, *args, **kwargs)\n\n File \"C:\\Python27\\lib\\site-packages\\django\\db\\models\\query.py\", line 642, in _filter_or_exclude\n clone.query.add_q(Q(*args, **kwargs))\n\n File \"C:\\Python27\\lib\\site-packages\\django\\db\\models\\sql\\query.py\", line 1250, in add_q\n can_reuse=used_aliases, force_having=force_having)\n\n File \"C:\\Python27\\lib\\site-packages\\django\\db\\models\\sql\\query.py\", line 1122, in add_filter\n process_extras=process_extras)\n\n File \"C:\\Python27\\lib\\site-packages\\django\\db\\models\\sql\\query.py\", line 1316, in setup_joins\n \"Choices are: %s\" % (name, \", \".join(names)))\n\nFieldError: Cannot resolve keyword 'page_set' into field. Choices are: displayName, facebook, faculty, friend, id, major, n_id, name, page, password, picture, reporter, year_in_school\n"}

Answer 1

I have also been struggling with the same FieldError thrown from setup_joins, and I think I just solved my issue. I was trying to filter through a Many-to-Many relationship, and could never get the "_set" in fields.ToManyField() to work. After debugging the TastyPie code in the error case and in a working simple filter, I realized it may be possible to bypass the need for the intermediary resource altogether.
Here is what worked for me, I hope it helps in your situation. Since I don't know your model setup, I'll make up a similar example.
First, the models:
### models.py ###
from django.db import models
class Ingredient(models.Model):
name = models.CharField(max_length=100)
description = models.TextField()
def __unicode__(self):
return '%s' % (self.name)
class RecipeIngredient(models.Model):
recipe = models.ForeignKey('Recipe')
ingredient = models.ForeignKey('Ingredient')
weight = models.IntegerField(null = True, blank = True)
def __unicode__(self):
return '%s: %s' % (self.recipe, self.ingredient)
class Recipe(models.Model):
title = models.CharField(max_length=100)
ingredients = models.ManyToManyField(Ingredient, through='RecipeIngredient')
def __unicode__(self):
return '%s' % (self.title)
And here are the ModelResources:
### api.py ###
from tastypie.resources import ModelResource, ALL, ALL_WITH_RELATIONS
from tastypie import fields
from some_app.models import Ingredient, Recipe
class IngredientResource(ModelResource):
class Meta:
queryset = Ingredient.objects.all()
resource_name = 'ingredient'
filtering = {
'name': ALL,
}
class RecipeResource(ModelResource):
ingredients = fields.ToManyField(
'some_app.api.IngredientResource',
'ingredients',
full=True)
class Meta:
queryset = Recipe.objects.all()
resource_name = 'recipe'
filtering = {
'title': ALL,
'ingredients': ALL_WITH_RELATIONS,
}
Notice I do not have a RecipeIngredientResource, I hook directly to the IngredientResource, which works because the Recipe model includes the ManyToManyField ingredients with the option through='RecipeIngredient'
An example URL to filter all recipes for a particular ingredient then looks like:
http://localhost:8000/api/recipes/recipe/?ingredients__name=blueberry
And, for completeness, here's a fixture for a Django app named 'some_app' to save time entering data for anyone wanting to implement this example:
[
{
"pk": 1,
"model": "some_app.ingredient",
"fields": {
"name": "apple",
"description": "a tempting fruit"
}
},
{
"pk": 2,
"model": "some_app.ingredient",
"fields": {
"name": "cherry",
"description": "a red fruit"
}
},
{
"pk": 3,
"model": "some_app.ingredient",
"fields": {
"name": "blueberry",
"description": "a blue fruit"
}
},
{
"pk": 4,
"model": "some_app.ingredient",
"fields": {
"name": "flour",
"description": "used for baking and stuff"
}
},
{
"pk": 5,
"model": "some_app.ingredient",
"fields": {
"name": "sugar",
"description": "makes stuff sweet"
}
},
{
"pk": 1,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 1,
"weight": 3,
"ingredient": 1
}
},
{
"pk": 2,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 1,
"weight": 2,
"ingredient": 4
}
},
{
"pk": 3,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 1,
"weight": 4,
"ingredient": 5
}
},
{
"pk": 4,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 2,
"weight": 8,
"ingredient": 2
}
},
{
"pk": 5,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 2,
"weight": 4,
"ingredient": 4
}
},
{
"pk": 6,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 2,
"weight": 6,
"ingredient": 5
}
},
{
"pk": 7,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 3,
"weight": 15,
"ingredient": 3
}
},
{
"pk": 8,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 3,
"weight": 5,
"ingredient": 4
}
},
{
"pk": 9,
"model": "some_app.recipeingredient",
"fields": {
"recipe": 3,
"weight": 6,
"ingredient": 5
}
},
{
"pk": 1,
"model": "some_app.recipe",
"fields": {
"title": "Apple Pie"
}
},
{
"pk": 2,
"model": "some_app.recipe",
"fields": {
"title": "Cherry Pie"
}
},
{
"pk": 3,
"model": "some_app.recipe",
"fields": {
"title": "Blueberry Pie"
}
}
]

Answer 2

This is the thing, if django tastypie works very similar to django (as anyone could expect) you are using a bad keyword, in you case, It wouldn't be page_set, use just page instead and it will work.
I recommend to you using a plural in the field name
pages = fields.ToManyField('chula.api.PageResource','page_set',null=True)
so the forward relation is pages and the backward relation is page_set I cant remember which now. But anyway it will look nicer.