CODEWITHSUNDEEP
javascriptrshinyselectize.js
pieca
pieca

Reputation: 2563

R Shiny selectizeInput: set minimum for amount of inputs

I have a selectizeInput with multiple = TRUE in a shiny application and I would like to prevent the user from selecting NULL (i.e., from leaving it blank). My goal is to ensure that at least one item is selected (no matter which one).

I found this question on the opposite problem (i.e., limiting maximum number of selections) and I checked selectize documentation. Unfortunately, there seem to be no minItems option. Is there a way to achieve my desired functionality?

Minimum example:

library(shiny)
shinyApp(

  ui = fluidPage(
    selectizeInput(
      inputId = "testSelect",
      label = "Test",
      choices = LETTERS[1:4],
      selected = LETTERS[1],
      multiple = TRUE,
      # Problem: how to specify 'minItems' here
      options = list(maxItems = 2)
    ),
    verbatimTextOutput("selected")
  ),

  server = function(input, output) {
    output$selected <- renderPrint({
      input$testSelect
    })
  }

)

Upvotes: 3

Views: 1496

Answers (1)

Tonio Liebrand
Tonio Liebrand

Reputation: 17699

Seems to be an open issue: #https://github.com/selectize/selectize.js/issues/1228.

Concerning your R/Shiny implementation you could use a workaround with renderUI().

You would build the input on the server side and control the selected choices. Before you build the input on the server side you can check the current value and if it does not fulfill your requirement you can overwrite it:

selected <- input$testSelect
if(is.null(selected)) selected <- choices[1]

Reproducible example:

library(shiny)
choices <- LETTERS[1:4]  
shinyApp(
  ui = fluidPage(
    uiOutput("select"),
    verbatimTextOutput("selected")
  ),
  server = function(input, output) {
    output$selected <- renderPrint({
      input$testSelect
    })

    output$select <- renderUI({
      selected <- input$testSelect
      if(is.null(selected)) selected <- choices[1]
      selectizeInput(
        inputId = "testSelect",
        label = "Test",
        choices = choices,
        selected = selected,
        multiple = TRUE,
        options = list(maxItems = 2)
      )
    })
  }
)

Upvotes: 5

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