# 📣 Dash v1.11.0 Release - Introducing Pattern-Matching Callbacks **URL:** \ **Category:** Dash Python\ **Tags:** announcements\ **Created:** [April 10, 2020, 7:31pm UTC](https://community.plotly.com/t/dash-v1-11-0-release-introducing-pattern-matching-callbacks/37592 "2020-04-10T19:31:18Z")\ **Posts on this page:** 1\ **Showing post:** 7
**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:** [April 17, 2020, 6:42am UTC](https://community.plotly.com/t/dash-v1-11-0-release-introducing-pattern-matching-callbacks/37592/7 "2020-04-17T06:42:40Z")
I am also seeing this issue in one of my full apps. The weird thing is that i have numerous callbacks linked to components that do do not exist, but only a few of them are throwing the error. For now, i have used wildcards to silence the error for these components, > [@ReferenceError in multipage application](https://community.plotly.com/t/referenceerror-in-multipage-application/14497/8): > > While not a real solution to the problem (which i have not yet understood fully; it seems to happen only in some cases), i have come up with a workaround using the new Dash pattern matching callbacks in [megaphone Dash v1.11.0 Release - Introducing Pattern-Matching Callbacks](https://community.plotly.com/t/dash-v1-11-0-release-introducing-pattern-matching-callbacks/37592/7). Let’s say that the problematic callback looks like this, @app.callback(Output(SITE\_HEIGHT\_CACHE, 'data'), [Input(SITE\_HEIGHT\_SLIDER, 'value')]) def update\_site\_height(value): return value with th… It seems that the fix i came up with is essentially equal to the suggestion by @alexcjohnson 😄 . I am slightly split about it, though i like it much better than the toggle-visible-fix. From a logical point of view, it seems reasonable that a wildcard callback should be used whenever the number of components is not constant, which is in fact the case; there can be zero or one component. However, the syntax is more complex for wildcard ids, and it worked just fine before without. As this zero-or-one case is rather common, a simple syntax would be preferable. To my understanding, in Dash 1.10.0 (and lower), a callback was simply not fired, if none of the input elements were present. Is this wrong? And if it is true, is there any reason not just to do this again? --- _[View the full topic](https://community.plotly.com/t/dash-v1-11-0-release-introducing-pattern-matching-callbacks/37592)._