Dynamic Tab Panels

app.R

library(shiny)

################################################################################
#
# GLOBALS
#
################################################################################

# On application start, we'll randomly choose whether
# the viewer can see our super-secret Old Faithful tab
IS_AUTHORIZED_TO_VIEW <- sample(c(TRUE, FALSE), 1, FALSE)


################################################################################
#
# USER INTERFACE
#
################################################################################

ui <- fluidPage(
  titlePanel("The Magic Disappearing Tab!"),

  sidebarLayout(
    sidebarPanel(
      # We'll only display this input if the user is
      # authorized to view the Old Faithful tab
      if(IS_AUTHORIZED_TO_VIEW == TRUE) {
        sliderInput(
          inputId = "bins",
          label = "Number of bins:",
          min = 1,
          max = 50,
          value = 30
        )
      }
    ),
      
    mainPanel(
      # Note that the actual tab construction has been
      # moved entirely to the server
      uiOutput("tabsetPanel")
    )
  )
)


################################################################################
#
# SERVER
#
################################################################################

server <- function(input, output, session) {
  output$faithfulPlot <- renderPlot({
    x    <- faithful[, 2]  # Old Faithful Geyser data
    bins <- seq(min(x), max(x), length.out = input$bins + 1)
    
    # draw the histogram with the specified number of bins
    p <- hist(x, breaks = bins, col = 'darkgray', border = 'white')    
    return(p)
  })
  
  
  # We will use this to dynamically create only the tabs which
  # our user is authorized to view
  tabConstructor <- reactive({
    # We start by initializing an empty list
    myTabs <- list()
    
    # We can now iterate through each tab with individual
    # access permissions and only append it to our list
    # if the current user should be allowed to view it.
    if(IS_AUTHORIZED_TO_VIEW == TRUE) {
      myTabs[[length(myTabs) + 1]] <- tabPanel(
        "Old Faithful",
        plotOutput("faithfulPlot")
      )
    }
    
    # Any tabs that do not require special privileges to view
    # can be appended without any conditional logic
    myTabs[[length(myTabs) + 1]] <- tabPanel(
      "F.A.Q."
    )
    
    return(myTabs)
  })
  
  output$tabsetPanel <- renderUI({
    # Here we're actually creating the tabsetPanel
    # object that will be rendered in the UI. The
    # `do.call()` function call takes two arguments:
    # the parent function we're calling (here,
    # `tabsetPanel()`), and any additional arguments
    # passed to that parent function (here, our list
    # of tabPanels). This is then rendered in the UI
    # file with a `uiOutput()` call.
    do.call(tabsetPanel, tabConstructor())
  })
}

# Run the application 
shinyApp(ui = ui, server = server)