From f22c67e48c9156ae0616611e3561f8b97fe8bb56 Mon Sep 17 00:00:00 2001
From: Dong-hyeon Shin <52447545+qu3vipon@users.noreply.github.com>
Date: Sat, 28 Jan 2023 10:18:54 +0900
Subject: [PATCH] Type check event handler signature (#363)

---
 pynecone/utils.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pynecone/utils.py b/pynecone/utils.py
index 48709a5ae..f8c376700 100644
--- a/pynecone/utils.py
+++ b/pynecone/utils.py
@@ -1127,8 +1127,15 @@ def get_handler_args(event_spec: EventSpec, arg: Var) -> Tuple[Tuple[str, str],
 
     Returns:
         The handler args.
+
+    Raises:
+        TypeError: If the event handler has an invalid signature.
     """
     args = inspect.getfullargspec(event_spec.handler.fn).args
+    if len(args) < 2:
+        raise TypeError(
+            f"Event handler has an invalid signature, needed a method with a parameter, got {event_spec.handler}."
+        )
     return event_spec.args if len(args) > 2 else ((args[1], arg.name),)