The app below contains a radio button group labelled Options and a renderUI expression that renders:
- an input element
input$datawhich depends on the value of the selected button and - an actionButton
input$add.
I would like to disable the button until the user selects a valid value for input$data. I tied observe({ toggleState(id = 'add', condition = !is.null(input$data)) }) but this fails. Printing the value of input$data to the console shows that the pickerInput initializes with two separate values NULL and "":
NULL
[1] ""
and so !is.null(input$data) returns:
[1] FALSE
[1] TRUE
Instead of just FALSE.
The app:
library(shiny)
library(shinyjs)
library(shinyWidgets)
ui <- fluidPage(shinyjs::useShinyjs(),
prettyRadioButtons('opt', label = 'Options', choices = c('state', 'file', 'letters')),
uiOutput('upload')
)
server <- shinyServer(function(input, output, session) {
output$upload = renderUI({
tagList(
switch(input$opt,
'state' = pickerInput('data', 'Choose a state',
choices = state.name,
options = list(title = "States..."),
choicesOpt = list(subtext = seq_along(state.name))
),
'file' = fileInput('data', 'Select file'),
'letters' = pickerInput('data', 'Choose a letter',
choices = LETTERS,
options = list(title = "Letters..."),
choicesOpt = list(subtext = seq_along(LETTERS))
)
),
actionButton('add', 'Add')
)
})
observe({
print(input$data) # pickerInput initializes with two values
toggleState(id = 'add', condition = !is.null(input$data))
})
})
shinyApp(ui, server)
Also, when you switch the radio button from the default selection of state to file and then back to state, the pickerInput returns just [1] "" (not the
NULL
[1] ""
that it returns on startup). I'm not sure what's going on here and I couldn't find anything relating to this in the documentation for pickerInput so any help would be greatly appreciated.
