Well, as far as I know, in Django you need to have abstract base classes for
models
(https://docs.djangoproject.com/en/1.10/topics/db/models/#model-inheritance
<https://docs.djangoproject.com/en/1.10/topics/db/models/#model-inheritance>).
If I understand your case correctly, NamedEntity and Entity contain some common
fields/methods, that should be present in all children. So you should make them
abstract and use them like this:
from django.db import models
class Entity(models.Model):
common_field = models.CharField(max_length=100) # some common field for
all children
class Meta:
abstract = True
class CustomEntity(Entity):
custom_field = models.CharField(max_length=100) # only present in
CostomEntities
# CustomEntity also has common_field in this example, so you could do that:
ce = CustomEntity(common_field='foo', custom_field='bar')
ce.save()
# But you can't do that with abstract models:
Entity(common_field='baz').save() # will raise an exception
So in your case there're three abstract models: Entity -> NamedEntity ->
SpeedyComposerNamedEntity -> (non-abstract models go here)
All abstract models have to have "abstract = True" attribute in their Meta
classes.
Here's a real life example from my project (I needed created/updated fields for
some of my models):
from django.db.models import Mode, DateTimeField
class TrackedModel(Model):
created = DateTimeField(auto_now_add=timezone.now)
modified = DateTimeField(auto_now=True)
class Meta:
abstract = True
class Event(TrackedModel):
description = ...
...
To reiterate, abstract models can't be saved like usual ones. So you can't use
Entity for base class and also to store some data in DB. Probably need another
level ob abstraction here.
> On 13 Dec 2016, at 19:18, Uri Even-Chen <u...@speedy.net> wrote:
>
> If I set SpeedyComposerNamedEntity to be abstract (which makes sense, there
> will not be objects of it), I get this error message:
>
> peedy\composer>manage.py makemigrations
> SystemCheckError: System check identified some issues:
>
> ERRORS:
> compose.Composition.accompaniment: (models.E006) The field 'accompaniment'
> clashes with the field 'accompaniment' from model 'accounts.namedentity'.
> compose.Composition.folder: (models.E006) The field 'folder' clashes with the
> field 'folder' from model 'accounts.namedentity'.
> compose.Composition.user: (models.E006) The field 'user' clashes with the
> field 'user' from model 'accounts.entity'.
> compose.Folder.user: (models.E006) The field 'user' clashes with the field
> 'user' from model 'accounts.entity'.
>
> And if I set NamedEntity to be abstract, I get this error message:
>
> speedy\composer>manage.py makemigrations
> SystemCheckError: System check identified some issues:
>
> ERRORS:
> compose.Composition.accompaniment: (models.E006) The field 'accompaniment'
> clashes with the field 'accompaniment' from model 'accounts.entity'.
> compose.Composition.folder: (models.E006) The field 'folder' clashes with the
> field 'folder' from model 'accounts.entity'.
> compose.Composition.user: (models.E006) The field 'user' clashes with the
> field 'user' from model 'accounts.entity'.
> compose.Folder.user: (models.E006) The field 'user' clashes with the field
> 'user' from model 'accounts.entity'.
>
> Entity can't be abstract because it contains all the entities and usernames
> on the database, it must have a table.
>
> Thanks,
> Uri.
>
>
> Uri Even-Chen
> Phone: +972-54-3995700 <tel:+972-54-3995700>
> Email: u...@speedy.net <mailto:u...@speedy.net>
> Website: http://www.speedysoftware.com/uri/en/
> <http://www.speedysoftware.com/uri/en/>
> <http://www.facebook.com/urievenchen> <http://plus.google.com/+urievenchen>
> <http://www.linkedin.com/in/urievenchen> <http://github.com/urievenchen>
> <http://twitter.com/urievenchen>
>
> On Tue, Dec 13, 2016 at 5:56 PM, GMail <robosl...@gmail.com
> <mailto:robosl...@gmail.com>> wrote:
> Hi!
>
> First guess - SpeedyComposerNamedEntity is not an abstract model. Meta is not
> inherited from NamedEntity, you have to do that explicitly:
>
> class SpeedyComposerNamedEntity(NamedEntity):
> ...
>
> class Meta(NamedEntity.Meta):
> pass
>
> ...
>
>
>> On 13 Dec 2016, at 18:30, Uri Even-Chen <u...@speedy.net
>> <mailto:u...@speedy.net>> wrote:
>>
>> Dear Django Users,
>>
>> I'm trying to write the models of Speedy Composer in Django 1.10.4, but I
>> can't run makemigrations - I get this error message:
>>
>> speedy\composer>manage.py makemigrations
>> SystemCheckError: System check identified some issues:
>>
>> ERRORS:
>> compose.Composition.accompaniment: (models.E006) The field 'accompaniment'
>> clashes with the field 'accompaniment' from model
>> 'compose.speedycomposernamedentity'.
>> compose.Composition.folder: (models.E006) The field 'folder' clashes with
>> the field 'folder' from model 'compose.speedycomposernamedentity'.
>> compose.Composition.user: (models.E006) The field 'user' clashes with the
>> field 'user' from model 'accounts.entity'.
>> compose.Folder.user: (models.E006) The field 'user' clashes with the field
>> 'user' from model 'accounts.entity'.
>>
>> This is my new models.py file of my new app, speedy.composer.compose (from
>> PyCharm):
>>
>> from django.conf import settings
>> from django.db import models
>> from django.utils.translation import ugettext_lazy as _
>>
>> from speedy.net.accounts.models import NamedEntity
>>
>>
>> class SpeedyComposerNamedEntity(NamedEntity):
>> MIN_USERNAME_LENGTH = 1
>> MAX_USERNAME_LENGTH = 200
>> MIN_SLUG_LENGTH = 1
>> MAX_SLUG_LENGTH = 200
>> MIN_NAME_LENGTH = 1
>> MAX_NAME_LENGTH = 200
>>
>> def __str__(self):
>> return '{}'.format(self.name)
>>
>>
>> class ChordsTemplate(SpeedyComposerNamedEntity):
>>
>> class Meta:
>> verbose_name = _('chords template')
>> verbose_name_plural = _('chords templates')
>>
>>
>> class Accompaniment(SpeedyComposerNamedEntity):
>>
>> class Meta:
>> verbose_name = _('accompaniment')
>> verbose_name_plural = _('accompaniments')
>>
>>
>> class Folder(SpeedyComposerNamedEntity):
>> user = models.ForeignKey(verbose_name=_('user'),
>> to=settings.AUTH_USER_MODEL, related_name='+')
>>
>> class Meta:
>> verbose_name = _('folder')
>> verbose_name_plural = _('folders')
>>
>>
>> class Composition(SpeedyComposerNamedEntity):
>> user = models.ForeignKey(verbose_name=_('user'),
>> to=settings.AUTH_USER_MODEL, related_name='+')
>> folder = models.ForeignKey(verbose_name=_('folder'), to=Folder,
>> related_name='+')
>> chords_template = models.ForeignKey(verbose_name=_('chords template'),
>> to=ChordsTemplate, related_name='+')
>> accompaniment = models.ForeignKey(verbose_name=_('accompaniment'),
>> to=Accompaniment, related_name='+')
>> tempo = models.SmallIntegerField(verbose_name=_('tempo'), default=105)
>> public = models.BooleanField(verbose_name=_('public'), default=False)
>>
>> class Meta:
>> verbose_name = _('composition')
>> verbose_name_plural = _('compositions')
>>
>> You can see the speedy.net <http://speedy.net/> code on GitHub:
>> https://github.com/urievenchen/speedy-net
>> <https://github.com/urievenchen/speedy-net>
>>
>> What did I do wrong? Did I write the models wrongly?
>> Thanks,
>> Uri.
>> Uri Even-Chen
>> Phone: +972-54-3995700 <tel:+972-54-3995700>
>> Email: u...@speedy.net <mailto:u...@speedy.net>
>> Website: http://www.speedysoftware.com/uri/en/
>> <http://www.speedysoftware.com/uri/en/>
>> <http://www.facebook.com/urievenchen>
>> <http://plus.google.com/+urievenchen>
>> <http://www.linkedin.com/in/urievenchen> <http://github.com/urievenchen>
>> <http://twitter.com/urievenchen>
>>
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