A callback with Custom Components?

whitphx · October 21, 2021, 4:22pm

Are there any way to implement the on_change callback with Custom Components?

whitphx · November 16, 2021, 11:37am

I understood it is currently impossible then I created a feature request:

github.com/streamlit/streamlit

A callback on a custom component

opened 01:21PM - 27 Oct 21 UTC

whitphx

enhancement

### Problem I am a developer of a custom component, [streamlit-webrtc](https:…//github.com/whitphx/streamlit-webrtc), which manages its state in Python code, and there is [a request](https://github.com/whitphx/streamlit-webrtc/issues/470) to make it possible to detect state changes through the `on_change` callback. However, currently a callback on a custom component is not supported. ### Solution * To introduce a mechanism to allow component developers to register and trigger a callback from a custom component. * It must not be an "automatic" trigger reacting to the changes of the frontend component state or session_state, such as a callback automatically invoked when the return value of `_component_func` or `session_state[key]` changes. * As stated above, my component manages the state on Python side and the component value differs from the returned value from the frontend component. Additionally, a value stored in the session state of its key is a mutable object so that it cannot be used to detect changes. So, I want a way to manually invoke the callback. * Ideally, it might be the best if we have a way to set arbitrary values to `WidgetMetadata.callback`, `WidgetMetadata.callback_args`, `WidgetMetadata.callback_kwargs`, and to forcefully call `call_callback(wid)` for a specific component. ### Additional context * Related feature request to my component: https://github.com/whitphx/streamlit-webrtc/issues/470

system · November 16, 2022, 11:38am

This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.

Topic		Replies	Views
Custom Component Callback before rerun Custom Components	1	668	December 9, 2022
Callbacks on custom components don't seem to be working in latest streamlit update Custom Components discussion	13	984	May 19, 2024
Am I right in assuming callbacks do not work for custom components in @st.experimental_dialog? - Callbacks broken in custom components Using Streamlit discussion , dialog	1	207	October 31, 2024
Send Event to React Component After Creating Custom Components	4	2093	February 3, 2023
Update component with latest session state Custom Components session-state	1	1441	August 6, 2023

A callback with Custom Components?

Related topics

Hello there 👋🏻

Cookie settings

Strictly necessary cookies

Performance cookies

Functional cookies

Targeting cookies