In Shiny apps for R, how do I delay the firing of a reactive?

Question

I have a selectizeInput in my Shiny app. It is in multiple-select mode, so the user can specify more than one selection.

However, the reactives that depend on the selectizeInput get fired every time a selection is added. Suppose that the user intends to select A, B and C. Currently, my app will do it expensive computations for the selections A, A, B and A, B, C, when only the last is required.

The best way I can think to solve this is to delay the firing of the selectizeInput by a second or so to give the user a chance to enter all of the selections. Each new selection should set the timer back to 1 second. I know that Shiny provides an invalidateLater command, but this causes the reactive to fire once now and once later.

How can I get the reactive to only fire once later?

Answer 1

You should debounce the reactive.

There is an R implementation here: https://gist.github.com/jcheng5/6141ea7066e62cafb31c