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Fixed #18478 - Documented how to use a mutable default in a model field.

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Tim Graham 2012-09-08 14:52:17 -04:00
parent 20ee727ac9
commit 6e2bb344e4
1 changed files with 8 additions and 0 deletions
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docs/ref/models/fields.txt
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@ -195,6 +195,14 @@ support tablespaces for indexes, this option is ignored.
The default value for the field. This can be a value or a callable object. If The default value for the field. This can be a value or a callable object. If
callable it will be called every time a new object is created. callable it will be called every time a new object is created.
The default cannot be a mutable object (model instance, list, set, etc.), as a
reference to the same instance of that object would be used as the default
value in all new model instances. Instead, wrap the desired default in a
callable. For example, if you had a custom ``JSONField`` and wanted to specify
a dictionary as the default, use a ``lambda`` as follows::
contact_info = JSONField("ContactInfo", default=lambda:{"email": "to1@example.com"})
``editable`` ``editable``
------------ ------------