Shiny dependent tabs

[MatStat]

I’m using shiny dashboard to create a GUI. My first tab in the sidebar will contain browsing function which uploads an excel file.
I’d like the second tab to contain a list using select button. The list is created by extracting data from the uploaded file. How do I put on hold the “select” button, until the first step is done?

Best

[MatStat]

When loading the app it gives me an error since the excel file wasn't uploaded yet in the first tab.
Does anyone have any experience with this?

[nirgrahamuk]

shiny has functions req()
as well as validate() and need() for handling requirements on downstream reactives.
I think in your case you would just add an appropraite req() call.
look at ?req in console for the documentation

[MatStat]

Thank you for replying I'll try to see if that helps.

Best