Django's Apps Source learning

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Django contains a registry of installed apps that store configuration information and a list of available models for introspection.

This registry is an application, located under Django.apps, essentially an instance of an apps class under the Django.apps.registry module.

See the truth before Source:

　　

Class Apps (object):

This is a registry that stores configuration information for installed apps and also tracks models, such as providing reverse-relations.

Primary properties of initialization:

Apps_configs: This is an ordered dictionary that maps the label label of the AppConfig instance to an already installed entry (AppConfig).

Main methods:

Populate (Installded_app): Loads the configuration information and model of the application, this method imports each application module and then each model module, which is thread-safe and idempotent (the impact of any number of executions is the same as the impact of a single execution), But can not re-enter (reentrant), simple Baidu, should be unable to make recursive call meaning.

　　

 ifSelf.ready: #该注册表是否已经被填充return        #populate () might is called by and threads in parallel on servers        #That create threads before initializing the WSGI callable.
# populate () can be called by two parallel threads on the server that will create the thread before the WSGI call is initialized. With Self._lock:
The #_lock () is a theading.lock () object that automatically acquires locks in the with context manager, after processing, and automatically releasing locks. ifSelf.ready:return            #App_config should be pristine, otherwise the code below won ' t            #Guarantee the order matches the order in Installed_apps.
# App_config should be in the original state, otherwise the following code will not guarantee that this order matches the order in Installed_apps.
            ifSelf.app_configs:RaiseRuntimeError ("populate () isn ' t reentrant")            #Phase 1:initialize app configs and import app modules.             forEntryinchInstalled_apps:
# iterate every item that has installed appsifisinstance (Entry, AppConfig): App_config=entryElse:
# If the Installed_apps is not configured with the Python path of the AppConfig class but the app module path, it will be created in Factory mode. App_config=appconfig.create (Entry)ifApp_config.labelinchSelf.app_configs:
# detects the uniqueness of the app_config. Raiseimproperlyconfigured ("application labels aren ' t unique,"                        "Duplicates:%s"%App_config.label) Self.app_configs[app_config.label]=the App_config # App_config.label property is obtained by default by App_name. App_config.apps=Self #将注册表赋给AppConfig类的apps属性. #Check for duplicate app names.Counts =Counter (App_config.name forApp_configinchself.app_configs.values ()) Duplicates=[Name forName, CountinchCounts.most_common ()ifCount > 1]            ifDuplicates:Raiseimproperlyconfigured ("application names aren ' t unique,"                    "Duplicates:%s"%", ". Join (Duplicates)) Self.apps_ready=True#Phase 2:import models modules.
# import Model Module
             forApp_configinchself.app_configs.values (): App_config.import_models () Self.clear_cache () self. Models_ready=True#Phase 3:run Ready () Methods of app Configs.
# Run the Ready () method of the apps configs.
             forApp_configinchself.get_app_configs (): App_config.ready () Self.ready= True

Django's Apps Source learning