diff options
| -rw-r--r-- | docs/topics/migrations.txt | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/docs/topics/migrations.txt b/docs/topics/migrations.txt index a188ea10c2..90e1a728a2 100644 --- a/docs/topics/migrations.txt +++ b/docs/topics/migrations.txt @@ -601,9 +601,14 @@ 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 @@ -611,8 +616,13 @@ from ``django.utils.deconstruct`` to add the method:: 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. |