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Code Issues 32 Releases Wiki Activity

[2.2.x] Clarified deconstruct() in Custom Model Field docs.

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Backport of 9fd90c4088 from master.
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David Beitey
2019-03-11 03:14:01 +00:00
committed by Tim Graham
parent 3e565b50a9
commit 282961f553
1 changed files with 8 additions and 5 deletions
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13
docs/howto/custom-model-fields.txt
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@@ -231,9 +231,10 @@ Field deconstruction
--------------------
The counterpoint to writing your ``__init__()`` method is writing the
``deconstruct()`` method. This method tells Django how to take an instance
of your new field and reduce it to a serialized form - in particular, what
arguments to pass to ``__init__()`` to re-create it.
:meth:`~.Field.deconstruct` method. It's used during :doc:`model migrations
</topics/migrations>` to tell Django how to take an instance of your new field
and reduce it to a serialized form - in particular, what arguments to pass to
``__init__()`` to re-create it.
If you haven't added any extra options on top of the field you inherited from,
then there's no need to write a new ``deconstruct()`` method. If, however,
@@ -269,8 +270,10 @@ we can drop it from the keyword arguments for readability::
del kwargs["max_length"]
return name, path, args, kwargs
If you add a new keyword argument, you need to write code to put its value
into ``kwargs`` yourself::
If you add a new keyword argument, you need to write code in ``deconstruct()``
that puts its value into ``kwargs`` yourself. You should also omit the value
from ``kwargs`` when it isn't necessary to reconstruct the state of the field,
such as when the default value is being used::
from django.db import models