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Code Issues Releases Wiki Activity

Simplified the implementation of register_model.

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register_model is called exactly once in the entire Django code base, at the
bottom of ModelBase.__new__:

    new_class._meta.apps.register_model(new_class._meta.app_label, new_class)

ModelBase.__new__ exits prematurely 120 lines earlier (sigh) if a model with
the same name is already registered:

    if new_class._meta.apps.get_registered_model(new_class._meta.app_label, name):
        return

(This isn't the exact code, but it's equivalent.)

apps.register_model and apps.get_registered_model are essentially a setter and
a getter for apps.all_models, and apps.register_model is the only setter. As a
consequence, new_class._meta.apps.all_models cannot change in-between.

Considering that name == new_class.__name__, we can conclude that
register_model(app_label, model) is always called with such arguments that
get_registered_model(app_label, model.__name__) returns None.

Considering that model._meta.model_name == model.__name__.lower(), and looking
at the implementation of register_model and get_registered_model, this proves
that self.all_models[app_label] doesn't contain model._meta.model_name in
register_model, allowing us to simplify the implementation.
This commit is contained in:
Aymeric Augustin 2013-12-27 23:03:03 +01:00
parent 3518e9ec1f
commit aff57793b4
1 changed files with 7 additions and 13 deletions
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20
django/apps/registry.py
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@ -261,19 +261,13 @@ class Apps(object):
# perform imports because of the risk of import loops. It mustn't
# call get_app_config().
model_name = model._meta.model_name
models = self.all_models[app_label]
if model_name in models:
# The same model may be imported via different paths (e.g.
# appname.models and project.appname.models). We use the source
# filename as a means to detect identity.
fname1 = os.path.abspath(upath(sys.modules[model.__module__].__file__))
fname2 = os.path.abspath(upath(sys.modules[models[model_name].__module__].__file__))
# Since the filename extension could be .py the first time and
# .pyc or .pyo the second time, ignore the extension when
# comparing.
if os.path.splitext(fname1)[0] == os.path.splitext(fname2)[0]:
return
models[model_name] = model
app_models = self.all_models[app_label]
# Defensive check for extra safety.
if model_name in app_models:
raise RuntimeError(
"Conflicting '%s' models in application '%s': %s and %s." %
(model_name, app_label, app_models[model_name], model))
app_models[model_name] = model
self.get_models.cache_clear()
def has_app(self, app_name):