Permalink
Browse files

Fixed #23473 -- Documented that @deconstructible classes need __eq__.

  • Loading branch information...
MarkusH authored and timgraham committed Sep 24, 2014
1 parent 450a616 commit 066e672d79ceb416ac87e51c8fa400221fa8604f
Showing with 12 additions and 2 deletions.
  1. +12 −2 docs/topics/migrations.txt
View
@@ -601,18 +601,28 @@ of three things ``(path, args, kwargs)``:
Django will write out the value as an instantiation of your class with the
given arguments, similar to the way it writes out references to Django fields.
+To prevent a new migration from being created each time
+:djadmin:`makemigrations` is run, you should also add a ``__eq__()`` method to
+the decorated class. This function will be called by Django's migration
+framework to detect changes between states.
+
As long as all of the arguments to your class' constructor are themselves
-serializable, you can just use the ``@deconstructible`` class decorator
-from ``django.utils.deconstruct`` to add the method::
+serializable, you can use the ``@deconstructible`` class decorator from
+``django.utils.deconstruct`` to add the ``deconstruct()`` method::
from django.utils.deconstruct import deconstructible
@deconstructible
class MyCustomClass(object):
def __init__(self, foo=1):
+ self.foo = foo
...
+ def __eq__(self, other):
+ return self.foo == other.foo
+
+
The decorator adds logic to capture and preserve the arguments on their
way into your constructor, and then returns those arguments exactly when
deconstruct() is called.

0 comments on commit 066e672

Please sign in to comment.