update README.md

Author: eadwinCode

README.md

@@ -33,5 +33,79 @@
 pip install ellar
 ```
 
+## Usage
+
+Create a file `controller.py`:
+
+```Python
+from ellar.common import ModuleRouter, Controller, get
+
+router = ModuleRouter('', tag='Math')
+
+
+@router.get("/add")
+def add(request, a: int, b: int):
+    return {"result": a + b}
+
+
+@Controller("", tag='Math')
+class MathAPI:
+
+    @get('/subtract', )
+    def subtract(self, a: int, b: int):
+        """Subtracts a from b"""
+        return {"result": a - b}
+
+    @get('/divide', )
+    def divide(self, a: int, b: int):
+        """Divides a by b"""
+        return {"result": a / b}
+
+    @get('/multiple', )
+    def multiple(self, a: int, b: int):
+        """Multiples a with b"""
+        return {"result": a * b}
+
+```
+
+Create another file `server.py`:
+
+```Python
+from ellar.core import AppFactory
+from ellar.openapi.builder import OpenAPIDocumentBuilder
+from ellar.openapi.module import OpenAPIDocumentModule
+from .controller import router, MathAPI
+
+
+app = AppFactory.create_app(routers=(router, ), controllers=(MathAPI, ))
+
+document_builder = OpenAPIDocumentBuilder()
+document_builder.set_title('Your Title')\
+    .set_version('1.0.2')\
+    .set_contact(name='Eadwin', url='https://www.yahoo.com', email='[email protected]')\
+    .set_license('MIT Licence', url='https://www.google.com')
+
+document = document_builder.build_document(app)
+module = app.install_module(OpenAPIDocumentModule, document=document)
+module.setup_swagger_doc()
+```
+
+### Interactive API docs
+
+Now go to <a href="http://localhost:8000/docs/" target="_blank">http://localhost:8000/docs/</a>
+
+You will see the automatic interactive API documentation (provided by <a href="https://github.com/swagger-api/swagger-ui" target="_blank">Swagger UI</a>):
+
+![Swagger UI](docs/img/ellar_demo.gif)
+
 ## Status
 Project is still in development
+- Remaining testing modules:
+    - common
+    - configuration
+    - guard
+    - openapi
+- Project CLI scaffolding
+- Database Plugin with [Encode/ORM](https://github.com/encode/orm)
+- Caching 
+- API Throttling

ellar/common/decorators/controller.py

@@ -82,7 +82,7 @@ def Controller(
     ] = None,
     include_in_schema: bool = True,
 ) -> t.Union[t.Type[ControllerBase], t.Callable[..., t.Any], t.Any]:
-    _prefix: t.Optional[t.Any] = prefix or NOT_SET
+    _prefix: t.Optional[t.Any] = prefix if prefix is not None else NOT_SET
     if prefix and isinstance(prefix, type):
         _prefix = NOT_SET