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Refs #12663 -- Removed Meta API upgrade guide.

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Tim Graham 2018-06-27 14:02:46 -04:00 committed by GitHub
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142
docs/ref/models/meta.txt
View File

@ -120,145 +120,3 @@ Retrieving all field instances of a model
<django.db.models.fields.DateTimeField: date_joined>,
<django.db.models.fields.related.ManyToManyField: groups>,
<django.db.models.fields.related.ManyToManyField: user_permissions>)
.. _migrating-old-meta-api:
Migrating from the old API
==========================
As part of the formalization of the ``Model._meta`` API (from the
:class:`django.db.models.options.Options` class), a number of methods and
properties have been deprecated and will be removed in Django 1.10.
These old APIs can be replicated by either:
* invoking :meth:`Options.get_field()
<django.db.models.options.Options.get_field()>`, or;
* invoking :meth:`Options.get_fields()
<django.db.models.options.Options.get_fields()>` to retrieve a list of all
fields, and then filtering this list using the :ref:`field attributes
<model-field-attributes>` that describe (or retrieve, in the case of
``_with_model`` variants) the properties of the desired fields.
Although it's possible to make strictly equivalent replacements of the old
methods, that might not be the best approach. Taking the time to refactor any
field loops to make better use of the new API - and possibly include fields
that were previously excluded - will almost certainly result in better code.
Assuming you have a model named ``MyModel``, the following substitutions
can be made to convert your code to the new API:
* ``MyModel._meta.get_field(name)`` becomes::
f = MyModel._meta.get_field(name)
then check if:
- ``f.auto_created == False``, because the new ``get_field()``
API will find "reverse" relations, and:
- ``f.is_relation and f.related_model is None``, because the new
``get_field()`` API will find
:class:`~django.contrib.contenttypes.fields.GenericForeignKey` relations.
* ``MyModel._meta.get_field_by_name(name)`` returns a tuple of these four
values with the following replacements:
- ``field`` can be found by ``MyModel._meta.get_field(name)``
- ``model`` can be found through the
:attr:`~django.db.models.Field.model` attribute on the field.
- ``direct`` can be found by: ``not field.auto_created or field.concrete``
The :attr:`~django.db.models.Field.auto_created` check excludes
all "forward" and "reverse" relations that are created by Django, but
this also includes ``AutoField`` and ``OneToOneField`` on proxy models.
We avoid filtering out these attributes using the
:attr:`concrete <django.db.models.Field.concrete>` attribute.
- ``m2m`` can be found through the
:attr:`~django.db.models.Field.many_to_many` attribute on the field.
* ``MyModel._meta.get_fields_with_model()`` becomes::
[
(f, f.model if f.model != MyModel else None)
for f in MyModel._meta.get_fields()
if not f.is_relation
or f.one_to_one
or (f.many_to_one and f.related_model)
]
* ``MyModel._meta.get_concrete_fields_with_model()`` becomes::
[
(f, f.model if f.model != MyModel else None)
for f in MyModel._meta.get_fields()
if f.concrete and (
not f.is_relation
or f.one_to_one
or (f.many_to_one and f.related_model)
)
]
* ``MyModel._meta.get_m2m_with_model()`` becomes::
[
(f, f.model if f.model != MyModel else None)
for f in MyModel._meta.get_fields()
if f.many_to_many and not f.auto_created
]
* ``MyModel._meta.get_all_related_objects()`` becomes::
[
f for f in MyModel._meta.get_fields()
if (f.one_to_many or f.one_to_one)
and f.auto_created and not f.concrete
]
* ``MyModel._meta.get_all_related_objects_with_model()`` becomes::
[
(f, f.model if f.model != MyModel else None)
for f in MyModel._meta.get_fields()
if (f.one_to_many or f.one_to_one)
and f.auto_created and not f.concrete
]
* ``MyModel._meta.get_all_related_many_to_many_objects()`` becomes::
[
f for f in MyModel._meta.get_fields(include_hidden=True)
if f.many_to_many and f.auto_created
]
* ``MyModel._meta.get_all_related_m2m_objects_with_model()`` becomes::
[
(f, f.model if f.model != MyModel else None)
for f in MyModel._meta.get_fields(include_hidden=True)
if f.many_to_many and f.auto_created
]
* ``MyModel._meta.get_all_field_names()`` becomes::
from itertools import chain
list(set(chain.from_iterable(
(field.name, field.attname) if hasattr(field, 'attname') else (field.name,)
for field in MyModel._meta.get_fields()
# For complete backwards compatibility, you may want to exclude
# GenericForeignKey from the results.
if not (field.many_to_one and field.related_model is None)
)))
This provides a 100% backwards compatible replacement, ensuring that both
field names and attribute names ``ForeignKey``\s are included, but fields
associated with ``GenericForeignKey``\s are not. A simpler version would be::
[f.name for f in MyModel._meta.get_fields()]
While this isn't 100% backwards compatible, it may be sufficient in many
situations.

10
docs/releases/1.8.txt
View File

@ -49,9 +49,7 @@ The ``Model._meta`` object has been part of Django since the days of pre-0.96
"Magic Removal" -- it just wasn't an official, stable API. In recognition of
this, we've endeavored to maintain backwards-compatibility with the old
API endpoint where possible. However, API endpoints that aren't part of the
new official API have been deprecated and will eventually be removed. A
:ref:`guide to migrating from the old API to the new API
<migrating-old-meta-api>` has been provided.
new official API have been deprecated and will eventually be removed.
Multiple template engines
-------------------------
@ -991,8 +989,7 @@ will work with both Django 1.8 and older versions::
for relation in opts.get_all_related_objects():
to_model = getattr(relation, 'related_model', relation.model)
Also note that ``get_all_related_objects()`` is deprecated in 1.8. See the
:ref:`upgrade guide <migrating-old-meta-api>` for the new API.
Also note that ``get_all_related_objects()`` is deprecated in 1.8.
Database backend API
--------------------
@ -1222,9 +1219,6 @@ deprecated and will be removed in Django 1.10:
* ``get_fields_with_model()``
* ``get_m2m_with_model()``
A :ref:`migration guide <migrating-old-meta-api>` has been provided to assist
in converting your code from the old API to the new, official API.
Loading ``cycle`` and ``firstof`` template tags from ``future`` library
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