feat: can declare listener as parameter too

onany/__init__.py

@@ -16,7 +16,10 @@ def disthread(event: str, *args, **kwargs) -> Thread:
     return thread
 
 
-def listener(event: str) -> callable:
+def listener(event: str, callback: callable = None) -> callable:
+    if callback:
+        return OnAny.listen(event, callback)
+
     def wrapper(callback: callable) -> None:
         return OnAny.listen(event, callback)
 

tests/generators.py

@@ -0,0 +1,16 @@
+from datetime import datetime
+
+
+print_history = {}
+
+def sprint(message: str) -> None:
+    print_history.update({
+        "last_print": message,
+        "history": print_history.get("history", []) + [{
+            "message": message,
+            "at": datetime.utcnow()
+        }]
+    })
+
+def get_last_sprint() -> str:
+    return print_history.get("last_print")

tests/test_onany.py

@@ -1,5 +1,6 @@
 from typing import Any, Dict
 from unittest import TestCase
+from tests.generators import sprint, get_last_sprint
 from onany import dispatch, disthread, listener
 
 
@@ -15,6 +16,16 @@ def test_dispatch_listen(self):
 
         self.assertTrue(params.get("called_once"))
 
+    def test_dispatch_listen_registering_simple_callback(self):
+        listener(
+            "event.name", 
+            lambda name: 
+                sprint("Hello {}. Welcome to OnAny!".format(name)))
+
+        dispatch("event.name", "Clark Kent")
+
+        self.assertEqual(get_last_sprint(), "Hello Clark Kent. Welcome to OnAny!")
+
     def test_thread_dispatch_listen(self):
         callback = self.get_listener()
         params = {