# Dash Extensions Blocking Callback Changed IDs

**URL:** <https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189>\
**Category:** Dash Python\
**Tags:** question\
**Created:** [November 23, 2022, 3:57pm UTC](https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189 "2022-11-23T15:57:38Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![jamie](https://avatars.discourse-cdn.com/v4/letter/j/aca169/32.png) [@jamie](https://community.plotly.com/u/jamie)\
**Post date:** [November 23, 2022, 3:57pm UTC](https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189/1 "2022-11-23T15:57:38Z")

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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

```auto
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

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**Author:** ![AIMPED](https://sea2.discourse-cdn.com/flex024/user_avatar/community.plotly.com/aimped/32/21758_2.png) [@AIMPED](https://community.plotly.com/u/AIMPED)\
**Post date:** [November 23, 2022, 4:23pm UTC](https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189/2 "2022-11-23T16:23:35Z")

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Hi @jamie welcome to the forums.

Take a look at this:

> [@Does the BlockingCallbackTransform dash extension work?](https://community.plotly.com/t/does-the-blockingcallbacktransform-dash-extension-work/70013):
>
> I tried to use the extension listed here: [BlockingCallbackTransform](https://www.dash-extensions.com/pages/transforms/blocking-callback-transform) 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.

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<div class="post-metadata">

**Author:** ![jamie](https://avatars.discourse-cdn.com/v4/letter/j/aca169/32.png) [@jamie](https://community.plotly.com/u/jamie)\
**Post date:** [November 23, 2022, 4:41pm UTC](https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189/3 "2022-11-23T16:41:23Z")

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

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**Author:** ![Emil](https://sea2.discourse-cdn.com/flex024/user_avatar/community.plotly.com/emil/32/31734_2.png) [@Emil](https://community.plotly.com/u/Emil)\
**Post date:** [November 23, 2022, 8:11pm UTC](https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189/4 "2022-11-23T20:11:54Z")

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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 😊

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<div class="post-metadata">

**Author:** ![jamie](https://avatars.discourse-cdn.com/v4/letter/j/aca169/32.png) [@jamie](https://community.plotly.com/u/jamie)\
**Post date:** [November 23, 2022, 9:01pm UTC](https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189/5 "2022-11-23T21:01:43Z")

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@Emil Thank you!

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**Author:** ![Emil](https://sea2.discourse-cdn.com/flex024/user_avatar/community.plotly.com/emil/32/31734_2.png) [@Emil](https://community.plotly.com/u/Emil)\
**Post date:** [November 29, 2022, 1:54pm UTC](https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189/6 "2022-11-29T13:54:49Z")

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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?

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<div class="post-metadata">

**Author:** ![jamie](https://avatars.discourse-cdn.com/v4/letter/j/aca169/32.png) [@jamie](https://community.plotly.com/u/jamie)\
**Post date:** [November 29, 2022, 3:55pm UTC](https://community.plotly.com/t/dash-extensions-blocking-callback-changed-ids/70189/7 "2022-11-29T15:55:29Z")

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