Bi-directional synchronization without triggering a loop

shiny
11

If there is a more egelant/powerfull approach to be found, id be happy to explore the ideas with you.
I think we are up to this proposal:

AppModel <- function() {
  self <- reactiveValues(
    name = NULL
  )

  return(self)
}

AppModel_checkCompleteness <- function(self) {
  incomplete <- list(
    name = NULL,
    completed = TRUE
  )

  if (is.null(self$name) || stringr::str_length(stringr::str_trim(self$name)) == 0) {
    incomplete$name <- "You have not specified your name"
    incomplete$completed <- FALSE
  }

  return(incomplete)
}


ui <- function() {
  view <- wellPanel(
    style = "width: 70%; margin-left: auto; margin-right: auto",
    textInput(
      "nameText",
      "Your name and surname",
      placeholder = "Please write your name and surname"
    ),
    textInput(
      "simulatesaved",
      "simulatesaved",
      value = "john Smith"
    ),
    actionButton("restore_from_saved", "restore from saved"),
    textOutput("model_content"),
    uiOutput("checklistUi"),
  )
  return(view)
}

server <- function(input, output, session) {
  app_model <- AppModel()

  .generateChecklistUi <- function() {
    Sys.sleep(2)



    completed <- AppModel_checkCompleteness(app_model)

    if (completed$completed) {
      completion_widget <- paste0("model content: ", app_model$name)
    } else {
      completion_widget <- "model content: not valid"
    }
    return(completion_widget)
  }


  observeEvent(input$nameText, {
    app_model$name <- req(input$nameText)
  })

  observeEvent(input$restore_from_saved, {
    app_model$name <- input$simulatesaved
    updateTextInput(
      session = session,
      inputId = "nameText",
      value = app_model$name
    )
  })

  observeEvent(
    {
      completeness <- AppModel_checkCompleteness(app_model)
      return(completeness$completed)
    },
    {
      output$checklistUi <- renderUI(.generateChecklistUi())
    }
  )

  output$model_content <- renderPrint(app_model$name)
}

shinyApp(ui = ui, server = server)

but you had a concern about volume of code to push changes to individual UI widgets