lapply function using a numericInput parameter around an observeEvent in RShiny - r

Question

I would like to create many multiple selectize inputs which are connected with each other. In other words : if an item is selected in one of the selectizeinputs i would like that it disappears from the other selectizeinputs' choices. In addition, i would like that the number of selectize inputs corresponds to the number selected in a numericinput.
The example below is working. The only question I have left is on the following line :
X = 1:100, ####### QUESTION HERE
Instead of 1:100, i would like to put something like 1:input$ui_number but I have the following error in R :
Error in .getReactiveEnvironment()$currentContext() : Operation not allowed without an active reactive context.
And if I put a "reactive" or an "observe" function around the lapply, the observeEvent does not work anymore. Any trick for me ?
Thank you for your help !
modalities <- LETTERS[1:10]
library(shiny)
app <- shinyApp(
ui = tabPanel("Change modalities",
numericInput("ui_number", label="Number of modalities",min = 1, max = 4, value=3),
uiOutput("renderui")
),
server = function(input, output, session) {
output$renderui <- renderUI({
output = tagList()
for(i in 1:input$ui_number){
output[[i]] = tagList()
output[[i]][[1]] = selectizeInput(paste0("ui_mod_choose",i), label=paste0("Modality ",i),choices=modalities, multiple = TRUE)
}
return(output)
})
lapply(
X = 1:100, ####### QUESTION HERE
FUN = function(j){
observeEvent({
input[[paste0("ui_mod_choose",j)]]
},
{
sapply(1:input$ui_number,function(i){
vecteur <- do.call(c,lapply((1:input$ui_number)[-i],function(i){input[[paste0("ui_mod_choose",i)]]}))
updateSelectizeInput(session,paste0("ui_mod_choose",i),choices= modalities[!modalities %in% vecteur],selected = input[[paste0("ui_mod_choose",i)]])
})
},
ignoreNULL = FALSE)
}
)
observeEvent({
input$ui_num
},
{
sapply(1:nput$ui_num,function(i){
updateSelectizeInput(session,paste0("ui_mod_choose",i),choice= modalities,selected=NULL)
})
}
)
}
)
runApp(app)

Answer 1

You could have a single observe() instead of multiple observeEvent():
library(shiny)
modalities <- LETTERS[1:10]
ui = tabPanel("Change modalities",
numericInput("ui_number", label = "Number of modalities",
min = 1, max = 4, value = 3),
uiOutput("renderui"))
server = function(input, output, session) {
# Generate modalities select lists
output$renderui <- renderUI({
output = tagList()
for (i in seq_len(input$ui_number)) {
output[[i]] = selectizeInput(paste0("ui_mod_choose", i),
label = paste0("Modality ", i),
choices = modalities, multiple = TRUE)
}
return(output)
})
# Remove selected modalities from other select lists
observe({
n <- isolate(input$ui_number)
for (i in seq_len(n)) {
vecteur <- unlist(lapply((1:n)[-i], function(i)
input[[paste0("ui_mod_choose",i)]]))
updateSelectizeInput(session, paste0("ui_mod_choose",i),
choices = setdiff(modalities, vecteur),
selected = input[[paste0("ui_mod_choose",i)]])
}
})
}
runApp(shinyApp(ui, server))