Problem with makemigrations on Speedy Composer

[Uri Even-Chen]

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 code on GitHub: 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 Email: u...@speedy.net Website: http://www.speedysoftware.com/uri/en/

[GMail]

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

    

    ...

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[Uri Even-Chen]

Why does it have to be abstract? NamedEntity and Entity are also not abstract.

https://github.com/urievenchen/speedy-net/blob/master/speedy/net/accounts/models.py

Uri.

Uri Even-Chen

Phone: +972-54-3995700 Email: u...@speedy.net Website: http://www.speedysoftware.com/uri/en/

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[Uri Even-Chen]

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 Email: u...@speedy.net Website: http://www.speedysoftware.com/uri/en/

On Tue, Dec 13, 2016 at 5:56 PM, GMail <robo...@gmail.com> wrote:

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[GMail]

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).

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.

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