Bookmarking and modules

Shiny’s bookmarking works with modules. As with Shiny applications, if the state of your module’s outputs are fully determined by the state of the inputs at a given time, then no modifications are necessary. If bookmarking is enabled by the application, then it will work for the module.

This application contains a very simple module, and bookmarking works for it just by calling enableBookmarking() as we did in other applications:

# A simple module that captializes input text
capitalizerUI <- function(id) {
  ns <- NS(id)
  wellPanel(
    h4("Text captializer module"),
    textInput(ns("txt"), "Enter text:"),
    verbatimTextOutput(ns("out"))
  )
}
capitalizerServer <- function(input, output, session) {
  output$out <- renderText({
    toupper(input$txt)
  })
}

# Main app code
ui <- function(request) {
  fluidPage(
    capitalizerUI("tc"),
    bookmarkButton()
  )
}
server <- function(input, output, session) {
  callModule(capitalizerServer, "tc")
}
shinyApp(ui, server, enableBookmarking = "url")

If the bookmarking for the module requires customization, the API is the same as for a full Shiny application. Modules can have their own onBookmark, onRestore, and onRestored callbacks (they can’t have onBookmarked, because that one is meant to display UI for the app as a whole), and they can have their own set of excluded inputs by calling setBookmarkExclude(). Using these functions in the module will not affect the parent application, and vice versa.

In the following example, the module has its own input$text, as well as onBookmark and onRestore callbacks which store a value in state$values$hash. The main application also has input$text, as well as onBookmark and onRestore callbacks which store a value in state$values$hash. Even though the variable names look the same, Shiny’s module logic namespaces them and prevents the module’s code and application’s code from interfering with each other.

# A basic module that captializes text. When bookmarked, it saves the text and a
# hash of the text.
capitalizerUI <- function(id) {
  ns <- NS(id)
  wellPanel(
    h4("Text captializer module"),
    textInput(ns("text"), "Enter text:"),
    "Capitalized text:", 
    verbatimTextOutput(ns("out"))
  )
}
capitalizerServer <- function(input, output, session) {
  output$out <- renderText({
    toupper(input$text)
  })
  onBookmark(function(state) {
    state$values$hash <- digest::digest(input$text, "md5")
  })
  onRestore(function(state) {
    if (identical(digest::digest(input$text, "md5"), state$values$hash)) {
      showNotification(paste0('Module\'s input text "', input$text,
        '" matches hash ', state$values$hash))
    } else {
      showNotification(paste0('Module\'s input text "', input$text,
        '" does not match hash ', state$values$hash))
    }
  })
}

# The main application calls the module, and also saves its own text and a hash
# of the text.
ui <- function(request) {
  basicPage(
    capitalizerUI("tc"),
    h4("Main app"),
    textInput("text", "Enter text:"),
    "Verbatim text:",
    verbatimTextOutput("out"),
    bookmarkButton()
  )
}
server <- function(input, output, session) {
  callModule(capitalizerServer, "tc")

  output$out <- renderText({
    input$text
  })
  onBookmark(function(state) {
    state$values$hash <- digest::digest(input$text, "md5")
  })
  onRestore(function(state) {
    if (identical(digest::digest(input$text, "md5"), state$values$hash)) {
      showNotification(paste0('App\'s input text "', input$text,
        '" matches hash ', state$values$hash))
    } else {
      showNotification(paste0('App\'s input text "', input$text,
        '" does not match hash ', state$values$hash))
    }
  })
}
shinyApp(ui, server, enableBookmarking = "url")


If you have questions about this article or would like to discuss ideas presented here, please post on RStudio Community. Our developers monitor these forums and answer questions periodically. See help for more help with all things Shiny.


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