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153 lines
4.5 KiB
Plaintext
153 lines
4.5 KiB
Plaintext
.. _ref-validators:
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==========
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Validators
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==========
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.. versionadded:: 1.2
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Writing validators
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==================
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A validator is a callable that takes a value and raises a
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``ValidationError`` if it doesn't meet some criteria. Validators can be useful
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for re-using validation logic between different types of fields.
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For example, here's a validator that only allows even numbers::
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from django.core.exceptions import ValidationError
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def validate_even(value):
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if value % 2 != 0:
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raise ValidationError(u'%s is not an even number' % value)
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You can add this to a model field via the field's ``validators``
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argument::
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from django.db import models
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class MyModel(models.Model):
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even_field = models.IntegerField(validators=[validate_even])
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Because values are converted to Python before validators are run, you can even
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use the same validator with forms::
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from django import forms
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class MyForm(forms.Form):
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even_field = forms.IntegerField(validators=[validate_even])
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How validators are run
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======================
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See the :ref:`form validation <ref-forms-validation>` for more information on
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how validators are run in forms, and :ref:`Validating objects
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<validating-objects>` for how they're run in models. Note that validators will
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not be run automatically when you save a model, but if you are using a
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``ModelForm``, it will run your validators on any fields that are included in
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your form. See the :ref:`ModelForm documentation <topics-forms-modelforms>`
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for information on how model validation interacts with forms.
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Built-in validators
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===================
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Django has a collection of callable validators for use with model and form
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fields. They're used internally but are available for use with your own fields,
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too. They can be used in addition to, or in lieu of custom ``field.clean()``
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methods.
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``RegexValidator``
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------------------
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.. class:: RegexValidator(regex=None, message=None, code=None)
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.. attribute:: regex=None
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The regular expression pattern to search for the provided ``value``. Raises a
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``ValidationError`` with ``message`` and ``code`` if no match is found. If
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no regex is specified, an empty string is used.
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.. attribute:: message=None
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The error message used by ``ValidationError`` if validation fails. If no
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``message`` is specified, a generic ``"Enter a valid value"`` message is used.
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.. attribute:: code=None
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The error code used by ``ValidationError`` if validation fails. If ``code``
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is not specified, ``"invalid"`` is used.
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``URLValidator``
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----------------
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.. class:: URLValidator(verify_exists=False, validator_user_agent=URL_VALIDATOR_USER_AGENT)
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A ``RegexValidator`` that ensures a value looks like a URL and optionally
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verifies that the URL actually exists (i.e., doesn't return a 404 status code).
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Raises an error code of ``'invalid'`` if it doesn't look like a URL, and a code
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of ``'invalid_link'`` if it doesn't exist.
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.. attribute:: verify_exists=False
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If ``verify_exists`` is ``True``, this validator checks that the URL actually
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exists.
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.. attribute:: validator_user_agent=URL_VALIDATOR_USER_AGENT
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If ``verify_exists`` is ``True``, it uses ``validator_user_agent`` as the "User-agent"
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for the request. This defaults to ``settings.URL_VALIDATOR_USER_AGENT``.
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``validate_email``
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------------------
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A ``RegexValidator`` instance that ensures a value looks like an e-mail address.
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``validate_slug``
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-----------------
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A ``RegexValidator`` instance that ensures a value consists of only letters,
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numbers, underscores or hyphens.
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``validate_ipv4_address``
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-------------------------
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A ``RegexValidator`` instance that ensures a value looks like an IPv4 address.
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``validate_comma_separated_integer_list``
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-----------------------------------------
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A ``RegexValidator`` instance that ensures a value is a comma-separated list
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of integers.
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``MaxValueValidator``
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---------------------
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.. class:: MaxValueValidator(max_value)
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Raises a ``ValidationError`` with a code of ``'max_value'`` if ``value`` is
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greater than ``max_value``.
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``MinValueValidator``
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---------------------
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.. class:: MinValueValidator(min_value)
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Raises a ``ValidationError`` with a code of ``'min_value'`` if ``value`` is
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less than ``min_value``.
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``MaxLengthValidator``
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----------------------
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.. class:: MaxLengthValidator(max_length)
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Raises a ``ValidationError`` with a code of ``'max_length'`` if the length of
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``value`` is greater than ``max_length``.
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``MinLengthValidator``
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----------------------
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.. class:: MinLengthValidator(min_length)
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Raises a ``ValidationError`` with a code of ``'min_length'`` if the length of
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``value`` is less than ``min_length``.
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