title: Shiny - observe() triggered by dynamicaly generated inputs
body: <p>I have a shiny code that generates selectInputs and each of those selectInput generate the plot title. The problem is that I don't know how to trigger an observe() with dynamically generated buttons. The workaround I used was to write on the code the input[[]] trigger for each selectInput to start the observe. Is it possible to trigger the observe() from all generated inputs?</p>
  
  <pre><code>library(shiny)
  library(shinydashboard)
  
  
  ui &lt;- dashboardPage(
    dashboardHeader(title = "Dynamic selectInput"),
    dashboardSidebar(
      sidebarMenu(
        menuItemOutput("menuitem")
      )
    ),
    dashboardBody(
      numericInput("graph_tytle_num","Number of Graph Title elements",value = 1,min = 1,max = 10),
      uiOutput("graph_title"),
      plotOutput("plot")
    )
  )
  
  server &lt;- function(input, output, session) {
    output$menuitem &lt;- renderMenu({
      menuItem("Menu item", icon = icon("calendar"))
    })
  
  
    #elements of graphic titles  
    output$graph_title &lt;- renderUI({
      buttons &lt;- as.list(1:input$graph_tytle_num)
      buttons &lt;- lapply(buttons, function(i)
  
        column(3,
          selectInput(inputId = paste0("title_element",i),
                      label = paste("Title element",i),
                      choices = paste0(LETTERS[i],seq(1,i*2)),
                      selected = 1)
        )
      )
    })
  
  
    observe({
  
      #Can this observe be triggerd by the dynamicaly generate selectInput?
      #In this the observe is only triggered with the first 3 selectInput
      input[[paste0("title_element",1)]]
      input[[paste0("title_element",2)]]
      input[[paste0("title_element",3)]]
  
  
      isolate({ #I dont want to have the numericInput input$graph_tytle_num to be a trigger
  
        #Create the graph title
        title &lt;- c()
        for(i in 1:input[["graph_tytle_num"]]){
          title &lt;- paste(title,input[[paste0("title_element",i)]])
        }
  
        output$plot &lt;-renderPlot({hist(rnorm(100,4,1),
                                       breaks = 10,
                                       main = title)})
      })
    })
  }
  
  shinyApp(ui, server)
  </code></pre>