Creating a UI from a loop

server.R
ui.R

function(input, output, session) {

  # note we use the syntax input[['foo']] instead of input$foo, because we have
  # to construct the id as a character string, then use it to access the value;
  # same thing applies to the output object below
  output$a_out <- renderPrint({
    res <- lapply(1:5, function(i) input[[paste0('a', i)]])
    str(setNames(res, paste0('a', 1:5)))
  })

  lapply(1:10, function(i) {
    output[[paste0('b', i)]] <- renderUI({
      strong(paste0('Hi, this is output B#', i))
    })
  })
}

fluidPage(
  title = 'Creating a UI from a loop',

  sidebarLayout(
    sidebarPanel(
      # create some select inputs
      lapply(1:5, function(i) {
        selectInput(paste0('a', i), paste0('SelectA', i),
                    choices = sample(LETTERS, 5))
      })
    ),

    mainPanel(
      verbatimTextOutput('a_out'),

      # UI output
      lapply(1:10, function(i) {
        uiOutput(paste0('b', i))
      })
    )
  )
)