automatically initialize adapter + enforcer

README.md

@@ -28,38 +28,40 @@ Based on [Officially Supported Databases](https://docs.djangoproject.com/en/3.0/
 pip install casbin-django-orm-adapter
 ```
 
-Add `casbin_adapter` to your `INSTALLED_APPS`
+Add `casbin_adapter.apps.CasbinAdapterConfig` to your `INSTALLED_APPS`
 
 ```python
+# settings.py
+BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+
 INSTALLED_APPS = [
     ...
-    'casbin_adapter',
+    'casbin_adapter.apps.CasbinAdapterConfig',
     ...
 ]
+
+CASBIN_MODEL = os.path.join(BASE_DIR, 'casbin.conf')
 ```
 
-To run schema migration, execute `python manage.py migrate casbin_adapter
+To run schema migration, execute `python manage.py migrate casbin_adapter`
 
 ## Simple Example
 
 ```python
-import casbin
-from casbin_adapter.adapter import Adapter
-
-adapter = Adapter()
-
-e = casbin.Enforcer('path/to/model.conf', adapter, True)
-
-sub = "alice"  # the user that wants to access a resource.
-obj = "data1"  # the resource that is going to be accessed.
-act = "read"  # the operation that the user performs on the resource.
-
-if e.enforce(sub, obj, act):
-    # permit alice to read data1casbin_django_orm_adapter
-    pass
-else:
-    # deny the request, show an error
-    pass
+# views.py
+from casbin_adapter.enforcer import enforcer
+
+def hello(request):
+    sub = "alice"  # the user that wants to access a resource.
+    obj = "data1"  # the resource that is going to be accessed.
+    act = "read"  # the operation that the user performs on the resource.
+
+    if e.enforce(sub, obj, act):
+        # permit alice to read data1casbin_django_orm_adapter
+        pass
+    else:
+        # deny the request, show an error
+        pass
 ```
 
 ### Getting Help

casbin_adapter/adapter.py

@@ -1,3 +1,4 @@
+from django.conf import settings
 from casbin import persist
 
 from .models import CasbinRule

casbin_adapter/apps.py

@@ -1,5 +1,12 @@
 from django.apps import AppConfig
+from django.db import connection
+from django.db.utils import OperationalError, ProgrammingError
 
 
 class CasbinAdapterConfig(AppConfig):
     name = 'casbin_adapter'
+
+    def ready(self):
+        from .enforcer import initialize_enforcer
+        initialize_enforcer()
+

casbin_adapter/enforcer.py

@@ -0,0 +1,64 @@
+from django.conf import settings
+from django.db import connection
+from django.db.utils import OperationalError, ProgrammingError
+
+from casbin import Enforcer
+
+from .adapter import Adapter
+
+
+class ProxyEnforcer(Enforcer):
+    _initialized = False
+
+    def __init__(self, *args, **kwargs):
+        if self._initialized:
+            super().__init__(*args, **kwargs)
+
+    def _load(self):
+        if self._initialized == False:
+            self._initialized = True
+            model = getattr(settings, 'CASBIN_MODEL')
+            enable_log = getattr(settings, 'CASBIN_LOG_ENABLED', False)
+            adapter = Adapter()
+
+            super().__init__(model, adapter, enable_log)
+
+            watcher = getattr(settings, 'CASBIN_WATCHER', None)
+            if watcher:
+                self.set_watcher(watcher)
+
+            role_manager = getattr(settings, 'CASBIN_ROLE_MANAGER', None)
+            if role_manager:
+                self.set_role_manager(role_manager)
+
+    def __getattribute__(self, name):
+        safe_methods = ['__init__', '_load', '_initialized']
+        if not super().__getattribute__('_initialized') and name not in safe_methods:
+            initialize_enforcer()
+            if not super().__getattribute__('_initialized'):
+                raise Exception((
+                    "Calling enforcer attributes before django registry is ready. "
+                    "Prevent making any calls to the enforcer on import/startup"
+                ))
+
+        return super().__getattribute__(name)
+
+
+enforcer = ProxyEnforcer()
+
+
+def initialize_enforcer():
+    try:
+        with connection.cursor() as cursor:
+            cursor.execute(
+                """
+                SELECT app, name applied FROM django_migrations
+                WHERE app = 'casbin_adapter' AND name = '0001_initial';
+                """
+            )
+            row = cursor.fetchone()
+            if row:
+                enforcer._load()
+    except (OperationalError, ProgrammingError):
+        pass
+

tests/settings.py

@@ -1,3 +1,7 @@
+import os
+
+BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+
 SECRET_KEY = 'not-a-production-secret'
 
 INSTALLED_APPS = [
@@ -7,7 +11,7 @@
     "django.contrib.sessions",
     "django.contrib.messages",
     "django.contrib.staticfiles",
-    "casbin_adapter",
+    "casbin_adapter.apps.CasbinAdapterConfig",
     "tests",
 ]
 
@@ -37,3 +41,5 @@
 ]
 
 DATABASES = {"default": {"ENGINE": "django.db.backends.sqlite3", "NAME": ":memory:"}}
+
+CASBIN_MODEL = os.path.join(BASE_DIR, 'tests', 'rbac_model.conf')