shinyServer(function(input, output, session) {
  observe({
    # We'll use the input$controller variable multiple times, so save it as x
    # for convenience.
    x <- input$controller
    # This will change the value of input$inText, based on x
    updateTextInput(session, "inText", value = paste("New text", x))
    # Can also set the label, this time for input$inText2
    updateTextInput(session, "inText2",
      label = paste("New label", x),
      value = paste("New text", x))
  })
})Run the code above in your browser using DataLab