dynamically creating multiple server module objects results in duplicate named servers about shiny HOT 2 OPEN

Thank you for a very clear explanation and links @scal-o! As that blog pointed out, I have been pulling my hair out about it.

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Hi! A little clarification: what is causing the problem here are not the duplicated "server objects", but rather the observer objects that they create. Every time you call selectInputServer(*id*) you create a new observer object with a binding to the *id*-show_popup input. So every time you increase the numeric input, you create a new series of observers all bound to the respective *id*-show_popup inputs, and that's why the shinyalert gets triggered multiple times.

One thing you could do to avoid issues (like creating the wrong number of objects and then just having them lying around occupying space and possibly resources) is destroying all of the previously created observers and creating anew only the ones you actually need every time input$num changes. This can be done via the destroy() method of the observer objects. Here is an example of how you could do it.

In the module server, list all of the observers you create to the session$userData$choose_a_name list. This will make the observer objects visible from the main server function.

selectInputServer <- function(id) {
  moduleServer(id, function(input, output, session) {
    print(paste("server", id))
    
    session$userData$observers[[id]] <- observe({
      shinyalert::shinyalert(title = "Success!", text = {
        "It worked!!"
      }, type = "success")
      
    }) %>% bindEvent(input$show_popup, ignoreInit = TRUE)
    
  })
}

In the main server function, call the destroy method on every observer object listed in session$userData$choose_a_name, and then generate the observers you need with lapply.

server <- function(input, output, session) {
  
  observe({

    if (length(session$userData$observers) != 0) {
      session$userData$observers <- lapply(
        session$userData$observers,
        function(obs) obs$destroy())
    }

    lapply(1:input$num, function(i) {
      selectInputServer(paste0("select", i))
    })

  })
  
  output$selectInputs <- renderUI({
    lapply(1:input$num, function(i) {
      selectInputUI(paste0("select", i))
    })
  })
  
  
}

By using this method you would also not need the numModules counter.
You can read some documentation about observer methods at ?observe, in the value section.
You can read about the session$userData environment at ?session, in the value section.
For a perhaps more clear explanation of what the code above does, look into this.

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