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82 lines
2.9 KiB
Plaintext
=====================
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Model class reference
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=====================
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.. currentmodule:: django.db.models
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This document covers features of the :class:`~django.db.models.Model` class.
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For more information about models, see :doc:`the complete list of Model
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reference guides </ref/models/index>`.
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Attributes
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==========
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``DoesNotExist``
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----------------
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.. exception:: Model.DoesNotExist
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This exception is raised by the ORM when an expected object is not found.
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For example, :meth:`.QuerySet.get` will raise it when no object is found
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for the given lookups.
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Django provides a ``DoesNotExist`` exception as an attribute of each model
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class to identify the class of object that could not be found, allowing you
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to catch exceptions for a particular model class. The exception is a
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subclass of :exc:`django.core.exceptions.ObjectDoesNotExist`.
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``MultipleObjectsReturned``
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---------------------------
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.. exception:: Model.MultipleObjectsReturned
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This exception is raised by :meth:`.QuerySet.get` when multiple objects are
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found for the given lookups.
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Django provides a ``MultipleObjectsReturned`` exception as an attribute of
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each model class to identify the class of object for which multiple objects
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were found, allowing you to catch exceptions for a particular model class.
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The exception is a subclass of
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:exc:`django.core.exceptions.MultipleObjectsReturned`.
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``NotUpdated``
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--------------
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.. versionadded:: 6.0
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.. exception:: Model.NotUpdated
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This exception is raised when :ref:`a forced update
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<ref-models-force-insert>` of a :class:`~django.db.models.Model` instance
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does not affect any rows.
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Django provides a ``NotUpdated`` exception as an attribute of each model
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class to identify the class of object that could not be updated, allowing
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you to catch exceptions for a particular model class. The exception is a
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subclass of :exc:`django.core.exceptions.ObjectNotUpdated` and inherits
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from :exc:`django.db.DatabaseError` for backward compatibility reasons.
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``objects``
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-----------
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.. attribute:: Model.objects
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Each non-abstract :class:`~django.db.models.Model` class must have a
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:class:`~django.db.models.Manager` instance added to it.
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Django ensures that in your model class you have at least a
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default ``Manager`` specified. If you don't add your own ``Manager``,
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Django will add an attribute ``objects`` containing default
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:class:`~django.db.models.Manager` instance. If you add your own
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:class:`~django.db.models.Manager` instance attribute, the default one does
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not appear. Consider the following example::
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from django.db import models
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class Person(models.Model):
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# Add manager with another name
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people = models.Manager()
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For more details on model managers see :doc:`Managers
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</topics/db/managers>` and :ref:`Retrieving objects <retrieving-objects>`.
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