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Field Extensions
================
:synopsis: Field Extensions
Database model field extensions.
AutoSlugField
-------------
AutoSlugField will automatically create a unique slug
incrementing an appended number on the slug until it is unique. Inspired by
SmileyChris' Unique Slugify snippet.
AutoSlugField takes a `populate_from` argument that specifies which field, list of
fields, or model method the slug will be populated from, for instance::
slug = AutoSlugField(populate_from=['title', 'description', 'get_author_name'])
`populate_from` can traverse a ForeignKey relationship by using Django ORM syntax::
slug = AutoSlugField(populate_from=['related_model__title', 'related_model__get_readable_name'])
AutoSlugField uses Django's slugify_ function by default to "slugify" ``populate_from`` field.
.. _slugify: https://docs.djangoproject.com/en/dev/ref/utils/#django.utils.text.slugify
To provide custom "slugify" function you could either provide the function as
an argument to :py:class:`~AutoSlugField` or define your ``slugify_function``
method within a model.
1. ``slugify_function`` as an argument to :py:class:`~AutoSlugField`.
.. code-block:: python
# models.py
from django.db import models
from django_extensions.db.fields import AutoSlugField
def my_slugify_function(content):
return content.replace('_', '-').lower()
class MyModel(models.Model):
title = models.CharField(max_length=42)
slug = AutoSlugField(populate_from='title', slugify_function=my_slugify_function)
2. ``slugify_function`` as a method within a model class.
.. code-block:: python
# models.py
from django.db import models
from django_extensions.db.fields import AutoSlugField
class MyModel(models.Model):
title = models.CharField(max_length=42)
slug = AutoSlugField(populate_from='title')
def slugify_function(self, content):
return content.replace('_', '-').lower()
**Important.**
If you both provide ``slugify_function`` in a model class and
pass ``slugify_function`` to :py:class:`~AutoSlugField` field,
then model's ``slugify_function`` method will take precedence.
RandomCharField
---------------
AutoRandomCharField will automatically create a
unique random character field with the specified length. By default
upper/lower case and digits are included as possible characters. Given
a length of 8 that yields 3.4 million possible combinations. A 12
character field would yield about 2 billion. Below are some examples::
>>> RandomCharField(length=8, unique=True)
BVm9GEaE
>>> RandomCharField(length=4, include_alpha=False)
7097
>>> RandomCharField(length=12, include_punctuation=True)
k[ZS.TR,0LHO
>>> RandomCharField(length=12, lowercase=True, include_digits=False)
pzolbemetmok
CreationDateTimeField
---------------------
A ``DateTimeField`` that will automatically set its date when the object is first
saved to the database. Works in the same way as the auto_now_add keyword.
ModificationDateTimeField
-------------------------
A ``DateTimeField`` that will automatically set its date when an object is saved
to the database. Works in the same way as the auto_now keyword. It is possible
to preserve the current timestamp by setting update_modified to False::
>>> example = MyTimeStampedModel.objects.get(pk=1)
>>> print example.modified
datetime.datetime(2016, 3, 18, 10, 3, 39, 740349, tzinfo=<UTC>)
>>> example.save(update_modified=False)
>>> print example.modified
datetime.datetime(2016, 3, 18, 10, 3, 39, 740349, tzinfo=<UTC>)
>>> example.save()
>>> print example.modified
datetime.datetime(2016, 4, 8, 14, 25, 43, 123456, tzinfo=<UTC>)
It is also possible to set the attribute directly on the model, for example
when you don't use the TimeStampedModel provided in this package, or when you
are in a migration::
>>> example = MyCustomModel.objects.get(pk=1)
>>> print example.modified
datetime.datetime(2016, 3, 18, 10, 3, 39, 740349, tzinfo=<UTC>)
>>> example.update_modified=False
>>> example.save()
>>> print example.modified
datetime.datetime(2016, 3, 18, 10, 3, 39, 740349, tzinfo=<UTC>)
ShortUUIDField
---------------
A ``CharField`` which transparently generates a UUID and pass it to base57.
It result in shorter 22 characters values useful e.g. for concise, unambiguous
URLS. It's possible to get shorter values with length parameter: they are
not Universal Unique any more but probability of collision is still low.
JSONField
---------
A generic ``TextField`` that neatly serializes/unserializes JSON
objects seamlessly. Django 1.9 introduces a native JSONField for
PostgreSQL, which is preferred for PostgreSQL users on Django
1.9 and above.
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