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189 lines
6.9 KiB
189 lines
6.9 KiB
"Utilities for loading models and the modules that contain them." |
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from django.conf import settings |
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from django.core.exceptions import ImproperlyConfigured |
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from django.utils.datastructures import SortedDict |
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import sys |
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import os |
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import threading |
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__all__ = ('get_apps', 'get_app', 'get_models', 'get_model', 'register_models', |
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'load_app', 'app_cache_ready') |
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class AppCache(object): |
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""" |
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A cache that stores installed applications and their models. Used to |
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provide reverse-relations and for app introspection (e.g. admin). |
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""" |
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# Use the Borg pattern to share state between all instances. Details at |
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# http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66531. |
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__shared_state = dict( |
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# Keys of app_store are the model modules for each application. |
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app_store = SortedDict(), |
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|
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# Mapping of app_labels to a dictionary of model names to model code. |
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app_models = SortedDict(), |
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|
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# Mapping of app_labels to errors raised when trying to import the app. |
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app_errors = {}, |
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# -- Everything below here is only used when populating the cache -- |
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loaded = False, |
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handled = {}, |
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postponed = [], |
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nesting_level = 0, |
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write_lock = threading.RLock(), |
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) |
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def __init__(self): |
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self.__dict__ = self.__shared_state |
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def _populate(self): |
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""" |
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Fill in all the cache information. This method is threadsafe, in the |
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sense that every caller will see the same state upon return, and if the |
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cache is already initialised, it does no work. |
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""" |
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if self.loaded: |
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return |
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self.write_lock.acquire() |
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try: |
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if self.loaded: |
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return |
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for app_name in settings.INSTALLED_APPS: |
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if app_name in self.handled: |
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continue |
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self.load_app(app_name, True) |
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if not self.nesting_level: |
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for app_name in self.postponed: |
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self.load_app(app_name) |
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self.loaded = True |
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finally: |
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self.write_lock.release() |
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def load_app(self, app_name, can_postpone=False): |
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""" |
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Loads the app with the provided fully qualified name, and returns the |
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model module. |
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""" |
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self.handled[app_name] = None |
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self.nesting_level += 1 |
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mod = __import__(app_name, {}, {}, ['models']) |
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self.nesting_level -= 1 |
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if not hasattr(mod, 'models'): |
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if can_postpone: |
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# Either the app has no models, or the package is still being |
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# imported by Python and the model module isn't available yet. |
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# We will check again once all the recursion has finished (in |
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# populate). |
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self.postponed.append(app_name) |
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return None |
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if mod.models not in self.app_store: |
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self.app_store[mod.models] = len(self.app_store) |
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return mod.models |
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def app_cache_ready(self): |
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""" |
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Returns true if the model cache is fully populated. |
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Useful for code that wants to cache the results of get_models() for |
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themselves once it is safe to do so. |
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""" |
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return self.loaded |
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def get_apps(self): |
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"Returns a list of all installed modules that contain models." |
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self._populate() |
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# Ensure the returned list is always in the same order (with new apps |
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# added at the end). This avoids unstable ordering on the admin app |
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# list page, for example. |
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apps = [(v, k) for k, v in self.app_store.items()] |
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apps.sort() |
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return [elt[1] for elt in apps] |
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def get_app(self, app_label, emptyOK=False): |
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""" |
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Returns the module containing the models for the given app_label. If |
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the app has no models in it and 'emptyOK' is True, returns None. |
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""" |
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self._populate() |
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self.write_lock.acquire() |
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try: |
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for app_name in settings.INSTALLED_APPS: |
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if app_label == app_name.split('.')[-1]: |
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mod = self.load_app(app_name, False) |
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if mod is None: |
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if emptyOK: |
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return None |
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else: |
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return mod |
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raise ImproperlyConfigured, "App with label %s could not be found" % app_label |
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finally: |
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self.write_lock.release() |
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def get_app_errors(self): |
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"Returns the map of known problems with the INSTALLED_APPS." |
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self._populate() |
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return self.app_errors |
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def get_models(self, app_mod=None): |
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""" |
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Given a module containing models, returns a list of the models. |
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Otherwise returns a list of all installed models. |
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""" |
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self._populate() |
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if app_mod: |
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return self.app_models.get(app_mod.__name__.split('.')[-2], SortedDict()).values() |
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else: |
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model_list = [] |
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for app_entry in self.app_models.itervalues(): |
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model_list.extend(app_entry.values()) |
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return model_list |
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def get_model(self, app_label, model_name, seed_cache=True): |
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""" |
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Returns the model matching the given app_label and case-insensitive |
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model_name. |
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Returns None if no model is found. |
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""" |
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if seed_cache: |
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self._populate() |
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return self.app_models.get(app_label, SortedDict()).get(model_name.lower()) |
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def register_models(self, app_label, *models): |
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""" |
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Register a set of models as belonging to an app. |
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""" |
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for model in models: |
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# Store as 'name: model' pair in a dictionary |
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# in the app_models dictionary |
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model_name = model._meta.object_name.lower() |
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model_dict = self.app_models.setdefault(app_label, SortedDict()) |
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if model_name in model_dict: |
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# The same model may be imported via different paths (e.g. |
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# appname.models and project.appname.models). We use the source |
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# filename as a means to detect identity. |
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fname1 = os.path.abspath(sys.modules[model.__module__].__file__) |
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fname2 = os.path.abspath(sys.modules[model_dict[model_name].__module__].__file__) |
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# Since the filename extension could be .py the first time and |
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# .pyc or .pyo the second time, ignore the extension when |
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# comparing. |
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if os.path.splitext(fname1)[0] == os.path.splitext(fname2)[0]: |
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continue |
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model_dict[model_name] = model |
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cache = AppCache() |
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# These methods were always module level, so are kept that way for backwards |
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# compatibility. |
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get_apps = cache.get_apps |
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get_app = cache.get_app |
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get_app_errors = cache.get_app_errors |
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get_models = cache.get_models |
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get_model = cache.get_model |
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register_models = cache.register_models |
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load_app = cache.load_app |
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app_cache_ready = cache.app_cache_ready
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