Why I am getting:
Error: One or more models did not validate:
test.test: "unique_together" refers to slug. This is not
in the same model as the unique_together statement.
test.test: "unique_together" refers to version. This is not
in the same model as the unique_together statement.
I have such model definition:
class SlugVersion(models.Model):
class Meta:
abstract = True
unique_together = (('slug', 'version'),)
slug = models.CharField(db_index=True, max_length=10, editable=False)
version = models.IntegerField(db_index=True, editable=False)
class Base(SlugVersion):
name = models.CharField(max_length=10)
class Test(Base):
test = models.IntegerField()
I have Django 1.3.
It seems it is a bug in Django.
It's because Test is inheriting from Base using multi-table inheritance, which creates separate tables for the two models and links them with a OneToOne relationship. So the slug and version fields exist only in the Base table but not in the Test table.
Do you need Base to be non-abstract? In other words, will you create any actual Base objects? If you set it to be abstract, this error goes away.
Related
I'd like to add foreign keys to virtually every model in my app to allow different Sites. For this I think it would be nice to use decorators, because I will be able to only add those FKs under certain conditions (e.g. if Sites is installed).
Unfortunately my attempt doesn't do anything:
def add_site_fk_field(model_to_annotate: models.Model):
"""Add FK to Site to Model"""
model_to_annotate.site = models.ForeignKey(Site, on_delete=models.CASCADE)
return model_to_annotate
#add_site_fk_field
class Test(models.Model):
...
Is it somehow possible to do this? I prefet not to use abstract classes.
As I know you cant do it with decorator. But you can do that with creating an abstract base model class.
For example:
from django.db import models
class Site(models.Model):
name = models.CharField(max_length=60)
class AddSiteFkField(models.Model):
fk_site = models.ForeignKey(Site, on_delete=models.CASCADE)
class Meta:
abstract = True
class Test(AddSiteFkField):
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
I have some columns that are repeated in multiple models. is there any solution to place them somewhere and use it any model?
You can achieve this by creating base classes and inheriting them in your models.
Example:
class TimestampsModel(models.Model):
#classmethod
def get_fields(cls, fields: tuple):
return fields.__add__(('created_at', 'updated_at'))
created_at = models.DateTimeField(("created_at"), auto_now_add=True)
updated_at = models.DateTimeField(("updated_at"), auto_now=True)
You can also make it abstract and Django won't create migrations for this.
class Meta:
abstract = True
Finally, a model would be:
class Blog(baseModels.TimestampsModel):
class Meta:
db_table = "blog"
title = models.CharField(max_length=100)
The code
I have these models :
class Activity(models.Model):
is_child_friendly = models.BooleanField()
free_wifi = models.BooleanField()
parking_avilable = models.BooleanField()
class RouteOrdering(models.Model):
route_id = models.ForeignKey(Route, on_delete=models.CASCADE)
activity_id = models.ForeignKey(Activity, on_delete=models.CASCADE, related_name='tracks')
day = models.IntegerField()
order = models.IntegerField()
class Meta:
ordering = ['order']
And these Serializers:
class ActivitySerializer(serializers.ModelSerializer):
class Meta:
model = Activity
class RouteOrderingSerializer(serializers.ModelSerializer):
class Meta:
model = RouteOrdering
fields = ('id','day','order','route_id','activity_id','tracks')
The problem
I want the RouteOrderingSerializer to return also the activity with the same activity_id. For this I thought I should use nested serializers.
What I've tried
I've tried adding a nested serializer like so:
activity = ActivitySerializer( read_only=True)
But this resulted no output in the endpoint. I know this is not the use case presented in the documentation, and this is probably why its noy working.
Ill be glad to see what code will work to get this done :)
I'm not sure why you got an error when you tried the following code. I assumed it was a bug related to the _id ending, but everything works fine when I run it.
class ActivitySerializer(serializers.ModelSerializer):
class Meta:
model = Activity
class RouteOrderingSerializer(serializers.ModelSerializer):
activity_id = ActivitySerializer( read_only=True)
class Meta:
model = RouteOrdering
fields = ('id','day','order','route_id','activity_id','tracks')
While you can, I don't recommend using a name ending in _id for a relation in Django. The issue is that Django internally stores all foreign keys under their <relation_name>_id. This allows various nice things, such as setting <object>.<relation_name>_id to an integer id and saving the object vs setting <object>.<relation_name> to the entire related object (which may require a db lookup to get in the first place). The one place I find this behaviour not intuitive is in serializers, where the default is to represent the relation as "<relation_name>": <id> instead of "<relation_name>_id": <id>, though you can explicitly declare the <relation_name>_id field and either remove or nest the <relation_name> field separately.
If you rename your relations to not have the trailing _id, the following will work:
class ActivitySerializer(serializers.ModelSerializer):
class Meta:
model = Activity
class RouteOrderingSerializer(serializers.ModelSerializer):
activity = ActivitySerializer( read_only=True)
class Meta:
model = RouteOrdering
fields = ('id','day','order','route_id','activity','tracks')
(Note that declaring route instead of route_id would be more in line with the default behaviour, but less clear in my opinion)
Try this:
class ActivitySerializer(serializers.ModelSerializer):
class Meta:
model = Activity
class RouteOrderingSerializer(serializers.ModelSerializer):
activity_id = ActivitySerializer()
class Meta:
model = RouteOrdering
fields = ('id','day','order','route_id','activity_id')
Is there a way to build django models hierarchy like this?
class LikableObjectMixin(models.Model):
# mixin for all likable objects: posts, photos, etc
likers = models.ManyToManyField(Account)
class Meta:
abstract = True
def save():
super(LikableObjectMixin, self).save()
class Post(LikableObjectMixin, models.Model):
message = models.TextField(_('Post'))
author = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='posts', blank=True, null=True)
created = models.DateTimeField(auto_now_add=True)
Can south work with this kind of inheritance? Is this an appropriate way to build model hierarchy?
Django=1.5.1
Yes, it's perfectly fine. South will create proper m2m relations for all your models that inherit from your mixin. You don't even have to write save method explicitly. So:
class LikableObjectMixin(models.Model):
likers = models.ManyToManyField(Account)
class Meta:
abstract = True
class Post(LikableObjectMixin):
message = models.TextField(_('Post'))
I've created a mixin and inherited from it in some models. The problem is when I create a schema migration, the mixin's fields are there.
class MyMixin(object):
a_field = models.CharField(max_length=30, blank=True)
another_field = models.DateTimeField(blank=True, null=True)
class Meta:
abstract = True
class MyModel(models.Model, myMixin):
...
Any ideas?
Seem to have got it working using the following
class MyMixin(models.Model):
a_field = models.CharField(max_length=30, blank=True)
another_field = models.DateTimeField(blank=True, null=True)
class Meta:
abstract = True
class MyModel(myMixin, models.Model):
...
The changes are:
MyMixin inherits Model rather than object (despite many discussions around the place saying that mixins for django should inherit object rather than Model)
the order of inheritance for MyModel - the mixin has to come first