Database utils

Fields

This library includes several subclasses of django model fields.

StatusField

class djutils.db.fields.StatusField(models.IntegerField)

Field to store status of model instance, i.e. “LIVE”, “DRAFT”, “DELETED”. Used by the djutils.db.managers.PublishedManager to expose the published() method.

Example:

from django.db import models

from djutils.db.fields import StatusField
from djutils.db.managers import PublishedManager

class BlogEntry(models.Model):
    title = models.CharField(max_length=255)
    body = models.TextField()
    status = StatusField()

    objects = PublishedManager('status') # use the status field

To return only those blog entries whose status is LIVE, we can query the manager:

>>> published_blogs = BlogEntry.objects.published()

SmartSlugField

class djutils.db.fields.SmartSlugField(models.SlugField)

Field that generates unique slugs in the event of collisions, optionally accepting a date-field.

It attempts to automate several of the pain-points with SlugFields:

• collisions:

  if a slug is specified as unique, a collision can cause you to get IntegrityErrors in your database – if you’re using your slug fields with a date_field (i.e. /news/2010/mar/5/some-headline/) then you will want to validate uniqueness for that day only.

• autopopulation:

  a slug is generally a URL-friendly representation of another field, such as a headline or title

• truncation:

  slugs can be truncated in such a way as to not break up a word, so instead of “some-interesting-headli” you’d get “some-interesting”

• underscores or numbers:

  if a collision is encountered, you can either append underscores or use a number:

  underscores: "slug", "slug_", "slug__", "slug___"
  numbers: "slug", "slug-1", "slug-2", "slug-3"

__init__(self, source_field=None, date_field=None, split_on_words=False, underscores=True, *args, **kwargs)

Parameters:

• source_field – name of the field to use for autopopulation
• date_field – if provided, the date to use for validating unique-ness. if not specified, the slug field will be marked as “unique” in the database.
• split_on_words – if True, slug will be truncated at the nearest word-boundary instead of cutting off at the character limit
• underscores – if True, underscores will be appended to generate a unique slug - otherwise, numbers will be used (slug, slug-1, slug-2, etc)

Managers

This library contains the :class:PublishedManager class

PublishedManager

class djutils.db.managers.PublishedManager(models.Manager)

__init__(self, status_field='status')

Parameters:status_field – the name of the StatusField to use to determine the status of the model instances

published(self)

returns a queryset of model instances whose status is LIVE_STATUS.

Utils

A collection of miscellaneous database helpers.

djutils.db.utils.extract_rel_field(model, related_to)

returns the name of the field on model that contains a relation to the related_to model:

>>> extract_rel_field(User, Group)
'groups'