Return input as list in reactive shiny - dynamic UI in insert UI

Question

I'm using the code from a previous solution R shiny dynamic UI in insertUI

In my app right now, the inputs are rendered by the server and displayed as different elements/rows, like this

$row_1
[1] "LV1" "x1" "x2" "x3"

$row_2
[1] "LV2" "x4" "x5" "x6"

I am actually hoping to get something like this instead:

"LV1" "x1" "x2" "x3"
"LV2" "x4" "x5" "x6"

I tried a few things but I'm unsure as to how to change the handle() functions to get the output I want.

Screenshots and code:

If you try running the shiny app, you will see this:

Click on + LV button and then simply select LV1 and then multi-select x1 x2 x3 and so on.

This is how it would look like with the output:

Here's the complete code

library(shiny)

newlist <- as.list(c("LV1", "LV2", "x1", "x2", "x3", "x4", "x5", "x6"))

row_ui <- function(id) {
  ns <- NS(id)
  fluidRow(
 
     column(2,
           uiOutput(ns("ui_placeholder"))),
      column(2, 
           uiOutput(ns("ui_placeholder2"))
    )
  )
} 

row_server <- function(input, output, session) {
  
  
  return_value <- reactive({c(input$variable1, input$variable2)})
  ns <- session$ns
  output$ui_placeholder <- renderUI({
 
      selectInput(ns("variable1"), "LV:", choices = c(' ', newlist), selected = NULL)
      
  })
  
  output$ui_placeholder2 <- renderUI({
    selectInput(ns("variable2"), "Ind:", choices = c(' ', newlist), selected = NULL, multiple = TRUE)
  })
  
   list(return_value = return_value) 
}

ui <- fluidPage(  
  div(id="placeholder"),
  actionButton("addLine", "+ LV"),
  verbatimTextOutput("out"),
  verbatimTextOutput("listout5")
)



server <- function(input, output, session) {
  
  handler <- reactiveVal(list())
  observeEvent(input$addLine, {
    new_id <- paste("row", input$addLine, sep = "_")
    insertUI(
      selector = "#placeholder",
      where = "beforeBegin",
      ui = row_ui(new_id)
    )
    handler_list <- isolate(handler())
    new_handler <- callModule(row_server, new_id)
    handler_list <- c(handler_list, new_handler)
    names(handler_list)[length(handler_list)] <- new_id
    handler(handler_list)
  })
  
  output$out <- renderPrint({
    lapply(handler(), function(handle) {
      handle()
    })
  })
  
 
}

shinyApp(ui, server)

Answer 1

Try this:

output$out <- renderPrint({
    invisible(lapply(handler(), function(handle) {
      cat(paste0(paste0(handle(), collapse = " "), "\n"))
    }))
  })

handle() returns a list, the first call to paste0 creates one string, the second paste0 adds a new line so that all values from one module are on the same line. invisible prevents that the return value from lapply gets printed (only the sideeffect from cat is printed)