Refs #12663 -- Removed Meta API upgrade guide.
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Tim Graham
GitHub
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@ -120,145 +120,3 @@ Retrieving all field instances of a model
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<django.db.models.fields.DateTimeField: date_joined>,
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<django.db.models.fields.related.ManyToManyField: groups>,
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<django.db.models.fields.related.ManyToManyField: user_permissions>)
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.. _migrating-old-meta-api:
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Migrating from the old API
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==========================
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As part of the formalization of the ``Model._meta`` API (from the
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:class:`django.db.models.options.Options` class), a number of methods and
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properties have been deprecated and will be removed in Django 1.10.
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These old APIs can be replicated by either:
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* invoking :meth:`Options.get_field()
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<django.db.models.options.Options.get_field()>`, or;
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* invoking :meth:`Options.get_fields()
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<django.db.models.options.Options.get_fields()>` to retrieve a list of all
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fields, and then filtering this list using the :ref:`field attributes
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<model-field-attributes>` that describe (or retrieve, in the case of
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``_with_model`` variants) the properties of the desired fields.
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Although it's possible to make strictly equivalent replacements of the old
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methods, that might not be the best approach. Taking the time to refactor any
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field loops to make better use of the new API - and possibly include fields
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that were previously excluded - will almost certainly result in better code.
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Assuming you have a model named ``MyModel``, the following substitutions
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can be made to convert your code to the new API:
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* ``MyModel._meta.get_field(name)`` becomes::
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f = MyModel._meta.get_field(name)
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then check if:
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- ``f.auto_created == False``, because the new ``get_field()``
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API will find "reverse" relations, and:
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- ``f.is_relation and f.related_model is None``, because the new
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``get_field()`` API will find
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:class:`~django.contrib.contenttypes.fields.GenericForeignKey` relations.
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* ``MyModel._meta.get_field_by_name(name)`` returns a tuple of these four
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values with the following replacements:
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- ``field`` can be found by ``MyModel._meta.get_field(name)``
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- ``model`` can be found through the
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:attr:`~django.db.models.Field.model` attribute on the field.
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- ``direct`` can be found by: ``not field.auto_created or field.concrete``
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The :attr:`~django.db.models.Field.auto_created` check excludes
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all "forward" and "reverse" relations that are created by Django, but
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this also includes ``AutoField`` and ``OneToOneField`` on proxy models.
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We avoid filtering out these attributes using the
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:attr:`concrete <django.db.models.Field.concrete>` attribute.
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- ``m2m`` can be found through the
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:attr:`~django.db.models.Field.many_to_many` attribute on the field.
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* ``MyModel._meta.get_fields_with_model()`` becomes::
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[
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(f, f.model if f.model != MyModel else None)
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for f in MyModel._meta.get_fields()
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if not f.is_relation
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or f.one_to_one
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or (f.many_to_one and f.related_model)
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]
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* ``MyModel._meta.get_concrete_fields_with_model()`` becomes::
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[
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(f, f.model if f.model != MyModel else None)
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for f in MyModel._meta.get_fields()
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if f.concrete and (
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not f.is_relation
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or f.one_to_one
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or (f.many_to_one and f.related_model)
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)
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]
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* ``MyModel._meta.get_m2m_with_model()`` becomes::
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[
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(f, f.model if f.model != MyModel else None)
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for f in MyModel._meta.get_fields()
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if f.many_to_many and not f.auto_created
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]
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* ``MyModel._meta.get_all_related_objects()`` becomes::
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[
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f for f in MyModel._meta.get_fields()
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if (f.one_to_many or f.one_to_one)
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and f.auto_created and not f.concrete
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]
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* ``MyModel._meta.get_all_related_objects_with_model()`` becomes::
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[
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(f, f.model if f.model != MyModel else None)
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for f in MyModel._meta.get_fields()
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if (f.one_to_many or f.one_to_one)
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and f.auto_created and not f.concrete
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]
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* ``MyModel._meta.get_all_related_many_to_many_objects()`` becomes::
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[
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f for f in MyModel._meta.get_fields(include_hidden=True)
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if f.many_to_many and f.auto_created
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]
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* ``MyModel._meta.get_all_related_m2m_objects_with_model()`` becomes::
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[
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(f, f.model if f.model != MyModel else None)
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for f in MyModel._meta.get_fields(include_hidden=True)
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if f.many_to_many and f.auto_created
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]
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* ``MyModel._meta.get_all_field_names()`` becomes::
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from itertools import chain
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list(set(chain.from_iterable(
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(field.name, field.attname) if hasattr(field, 'attname') else (field.name,)
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for field in MyModel._meta.get_fields()
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# For complete backwards compatibility, you may want to exclude
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# GenericForeignKey from the results.
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if not (field.many_to_one and field.related_model is None)
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)))
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This provides a 100% backwards compatible replacement, ensuring that both
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field names and attribute names ``ForeignKey``\s are included, but fields
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associated with ``GenericForeignKey``\s are not. A simpler version would be::
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[f.name for f in MyModel._meta.get_fields()]
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While this isn't 100% backwards compatible, it may be sufficient in many
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situations.
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@ -49,9 +49,7 @@ The ``Model._meta`` object has been part of Django since the days of pre-0.96
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"Magic Removal" -- it just wasn't an official, stable API. In recognition of
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this, we've endeavored to maintain backwards-compatibility with the old
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API endpoint where possible. However, API endpoints that aren't part of the
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new official API have been deprecated and will eventually be removed. A
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:ref:`guide to migrating from the old API to the new API
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<migrating-old-meta-api>` has been provided.
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new official API have been deprecated and will eventually be removed.
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Multiple template engines
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-------------------------
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@ -991,8 +989,7 @@ will work with both Django 1.8 and older versions::
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for relation in opts.get_all_related_objects():
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to_model = getattr(relation, 'related_model', relation.model)
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Also note that ``get_all_related_objects()`` is deprecated in 1.8. See the
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:ref:`upgrade guide <migrating-old-meta-api>` for the new API.
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Also note that ``get_all_related_objects()`` is deprecated in 1.8.
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Database backend API
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--------------------
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@ -1222,9 +1219,6 @@ deprecated and will be removed in Django 1.10:
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* ``get_fields_with_model()``
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* ``get_m2m_with_model()``
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A :ref:`migration guide <migrating-old-meta-api>` has been provided to assist
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in converting your code from the old API to the new, official API.
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Loading ``cycle`` and ``firstof`` template tags from ``future`` library
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-----------------------------------------------------------------------
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