import os
from importlib import import_module
from django.core.exceptions import ImproperlyConfigured
from django.utils.module_loading import module_has_submodule
MODELS_MODULE_NAME = 'models'
[文档]class AppConfig:
"""Class representing a Django application and its configuration."""
def __init__(self, app_name, app_module):
# Full Python path to the application e.g. 'django.contrib.admin'.
self.name = app_name
# Root module for the application e.g. <module 'django.contrib.admin'
# from 'django/contrib/admin/__init__.py'>.
self.module = app_module
# Reference to the Apps registry that holds this AppConfig. Set by the
# registry when it registers the AppConfig instance.
self.apps = None
# The following attributes could be defined at the class level in a
# subclass, hence the test-and-set pattern.
# Last component of the Python path to the application e.g. 'admin'.
# This value must be unique across a Django project.
if not hasattr(self, 'label'):
self.label = app_name.rpartition(".")[2]
# Human-readable name for the application e.g. "Admin".
if not hasattr(self, 'verbose_name'):
self.verbose_name = self.label.title()
# Filesystem path to the application directory e.g.
# '/path/to/django/contrib/admin'.
if not hasattr(self, 'path'):
self.path = self._path_from_module(app_module)
# Module containing models e.g. <module 'django.contrib.admin.models'
# from 'django/contrib/admin/models.py'>. Set by import_models().
# None if the application doesn't have a models module.
self.models_module = None
# Mapping of lowercase model names to model classes. Initially set to
# None to prevent accidental access before import_models() runs.
self.models = None
def __repr__(self):
return '<%s: %s>' % (self.__class__.__name__, self.label)
def _path_from_module(self, module):
"""Attempt to determine app's filesystem path from its module."""
# See #21874 for extended discussion of the behavior of this method in
# various cases.
# Convert paths to list because Python's _NamespacePath doesn't support
# indexing.
paths = list(getattr(module, '__path__', []))
if len(paths) != 1:
filename = getattr(module, '__file__', None)
if filename is not None:
paths = [os.path.dirname(filename)]
else:
# For unknown reasons, sometimes the list returned by __path__
# contains duplicates that must be removed (#25246).
paths = list(set(paths))
if len(paths) > 1:
raise ImproperlyConfigured(
"The app module %r has multiple filesystem locations (%r); "
"you must configure this app with an AppConfig subclass "
"with a 'path' class attribute." % (module, paths))
elif not paths:
raise ImproperlyConfigured(
"The app module %r has no filesystem location, "
"you must configure this app with an AppConfig subclass "
"with a 'path' class attribute." % (module,))
return paths[0]
@classmethod
def create(cls, entry):
"""
Factory that creates an app config from an entry in INSTALLED_APPS.
"""
try:
# If import_module succeeds, entry is a path to an app module,
# which may specify an app config class with default_app_config.
# Otherwise, entry is a path to an app config class or an error.
module = import_module(entry)
except ImportError:
# Track that importing as an app module failed. If importing as an
# app config class fails too, we'll trigger the ImportError again.
module = None
mod_path, _, cls_name = entry.rpartition('.')
# Raise the original exception when entry cannot be a path to an
# app config class.
if not mod_path:
raise
else:
try:
# If this works, the app module specifies an app config class.
entry = module.default_app_config
except AttributeError:
# Otherwise, it simply uses the default app config class.
return cls(entry, module)
else:
mod_path, _, cls_name = entry.rpartition('.')
# If we're reaching this point, we must attempt to load the app config
# class located at <mod_path>.<cls_name>
mod = import_module(mod_path)
try:
cls = getattr(mod, cls_name)
except AttributeError:
if module is None:
# If importing as an app module failed, check if the module
# contains any valid AppConfigs and show them as choices.
# Otherwise, that error probably contains the most informative
# traceback, so trigger it again.
candidates = sorted(
repr(name) for name, candidate in mod.__dict__.items()
if isinstance(candidate, type) and
issubclass(candidate, AppConfig) and
candidate is not AppConfig
)
if candidates:
raise ImproperlyConfigured(
"'%s' does not contain a class '%s'. Choices are: %s."
% (mod_path, cls_name, ', '.join(candidates))
)
import_module(entry)
else:
raise
# Check for obvious errors. (This check prevents duck typing, but
# it could be removed if it became a problem in practice.)
if not issubclass(cls, AppConfig):
raise ImproperlyConfigured(
"'%s' isn't a subclass of AppConfig." % entry)
# Obtain app name here rather than in AppClass.__init__ to keep
# all error checking for entries in INSTALLED_APPS in one place.
try:
app_name = cls.name
except AttributeError:
raise ImproperlyConfigured(
"'%s' must supply a name attribute." % entry)
# Ensure app_name points to a valid module.
try:
app_module = import_module(app_name)
except ImportError:
raise ImproperlyConfigured(
"Cannot import '%s'. Check that '%s.%s.name' is correct." % (
app_name, mod_path, cls_name,
)
)
# Entry is a path to an app config class.
return cls(app_name, app_module)
[文档] def get_model(self, model_name, require_ready=True):
"""
Return the model with the given case-insensitive model_name.
Raise LookupError if no model exists with this name.
"""
if require_ready:
self.apps.check_models_ready()
else:
self.apps.check_apps_ready()
try:
return self.models[model_name.lower()]
except KeyError:
raise LookupError(
"App '%s' doesn't have a '%s' model." % (self.label, model_name))
[文档] def get_models(self, include_auto_created=False, include_swapped=False):
"""
Return an iterable of models.
By default, the following models aren't included:
- auto-created models for many-to-many relations without
an explicit intermediate table,
- models that have been swapped out.
Set the corresponding keyword argument to True to include such models.
Keyword arguments aren't documented; they're a private API.
"""
self.apps.check_models_ready()
for model in self.models.values():
if model._meta.auto_created and not include_auto_created:
continue
if model._meta.swapped and not include_swapped:
continue
yield model
def import_models(self):
# Dictionary of models for this app, primarily maintained in the
# 'all_models' attribute of the Apps this AppConfig is attached to.
self.models = self.apps.all_models[self.label]
if module_has_submodule(self.module, MODELS_MODULE_NAME):
models_module_name = '%s.%s' % (self.name, MODELS_MODULE_NAME)
self.models_module = import_module(models_module_name)
[文档] def ready(self):
"""
Override this method in subclasses to run code when Django starts.
"""
