Shiny: Request: allow deleting an input that was removed using `removeUI()`

Created on 9 Apr 2019 · 3Comments · Source: rstudio/shiny

Currently, when an input is removed using removeUI(), its UI is deleted from the DOM but the input still lives from the server's perspective. It would be great if it was possible to clear that input completely.

Personal opinion: I would want this to be the default behaviour, because an input that does not exist on the page should not exist in the server - it's a bit of a logical discrepancy - but that breaking change might cause a lot of trouble so perhaps adding a parameter to removeUI() to do this would be helpful.

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daattali

👍14

Most helpful comment

For anyone looking for a workaround until this gets implemented, my solution meanwhile it to set the value of any removed inputs to NULL using javascript, with Shiny.onInputChange("input", 'null')

daattali on 22 Apr 2019

👍3

All 3 comments

daattali on 22 Apr 2019

👍3

Here's a reprex of this issue:

library(shiny)
ui <- fluidPage(
  actionButton("rmv", "Remove UI"),
  textInput("txt", "This is no longer useful", "plop")
)

# Server logic
server <- function(input, output, session) {
  observeEvent(input$rmv, {
    removeUI(
      selector = "#txt"
    )
  })
  observe({
    invalidateLater(1000)
    print(input$txt)
  })
}

shinyApp(ui, server)

I definitely second the idea of removing the value from the input list if the input is not there anymore.

The removeUI() function which can remove any part of the UI has to be kept, but there could be a removeInput() function, to be more specific to target the inputs.

ColinFay on 29 Aug 2019

Just dropping a thought here. If you're managing the lifecycle of modules using objects from a bespoke class system, for example, R6, you can register your takedown code as the _finalizer_ function of the module object. The _finalizer_ function will run as the object is garbage collected.