Why does rx.call_script require a return statement.

[abdullahkhalids]

In the docs, there is the following example of using rx.call_script inside a State function.

class SoundEffectState(rx.State):
    @rx.background
    async def delayed_play(self):
        await asyncio.sleep(1)
        return rx.call_script("playFromStart(button_sfx)")

I have played around with it, and it seems that call_script is not executed if it is not part of a return statement. Why?

My particular use case is that I am adding a html canvas via rx.html and controlling it using browser javascript, called from event handlers of reflex buttons and fields. Inside one those event handlers, I would ideally like to go, "python code -> call_script -> more python code". But it seems this is not possible.

[masenf]

To send the event to the client and continue running on the backend, use yield instead of return.

Since the event has to run in the browser the event handler needs to return or yield the call_script from the backend.

If you need the call_script to execute on the frontend immediately, then the event handler must be decorated with @rx.background, otherwise the frontend will not process the yielded events until the current event handler returns its final update.

[abdullahkhalids]

Thanks. I kind of get the logic. Will test out to see if I can get a basic example working.