Hi, I am currently using a Blocking Callback Transform in my dash app, and am having trouble determining which prop triggered said callback. I am currently trying to get the changed prop id using this line of code changed_ids = [p['prop_id'] for p in dash.callback_context.triggered] but this gives me a prop_id of [{'prop_id': 'e3dbfba0-9d54-43f9-988b-de6e50207200_start_client.data', 'value': 1669217063820}] Is there a way to parse the callback context? Thanks

Hi @jamie welcome to the forums. Take a look at this: [image] Does the BlockingCallbackTransform dash extension work? Dash Python I tried to use the extension listed here: BlockingCallbackTransform The blocking functionality works, but the context stopped working on my callbacks. Instead of giving the name of the trigger for ctx.trigger_id, the blocking functionality causes it to delivere a different value instead. I’d like to use the extensions, but I’m concerned that I can’t because the trigger id doesn’t appear to work.

Thanks @AIMPED I didn’t see that post. Looks like I will have to work around this.

I am surprised to se two cases have this exact same issue at almost the same time. I’ll look into a solution when I get some time on my hands :blush:

I have started working on a solution and published it as dash-extensions==0.1.8rc1. Could you try to see, if it resolves your usecase?

@Emil thank you, this works great. Parsing the callback context now works with BlockingCallbackTransform! I appreciate it.

Dash Extensions Blocking Callback Changed IDs

Dash Python

AIMPED November 23, 2022, 4:23pm 2

Hi @jamie welcome to the forums.

Take a look at this:

Topic		Replies	Views
Does the BlockingCallbackTransform dash extension work? Dash Python question	6	637	November 29, 2022
How to use dash.callback_context in dynamic callbacks? Dash Python question	3	681	September 11, 2023
LookupError when trying to use dash.ctx.triggered_id in a DjangoDash app Dash Python	0	76	May 20, 2025
How can I use ctx.triggered w/ an ALL callback to identify a button Dash Python	3	2664	June 5, 2020
Prop_id='.' and Value=None in dash.callback_context.triggered even after button is clicked Dash Python	4	1785	July 22, 2021

Dash Extensions Blocking Callback Changed IDs

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