VnPy Futures Trading

WHENWhen registering event handlers

ACTIONuse a handler function signature compatible with Callable[[Event], None]

CONSEQUENCEIncompatible handler signature causes TypeError at runtime when event engine attempts to invoke the handler

WHENWhen instantiating EventEngine

ACTIONcall start() method before putting any events into the queue

CONSEQUENCEEvents put before start() are either lost or processed after unexpected delay, causing missed trading signals or delayed order execution

WHENWhen creating an app that integrates with the platform

ACTIONdefine engine_class attribute pointing to the corresponding BaseEngine subclass

CONSEQUENCEMissing engine_class causes AttributeError when MainEngine.add_app() attempts to instantiate the engine, breaking app integration