shinydashboard error message "Expected an object with class 'shiny.tag"

Question

I am trying to create a dynamic notification on header on a shinyapp, and get an error message as Warning: Error in FUN: Expected an object with class 'shiny.tag'. The code is as below,

library(shiny)
library(shinydashboard)

ui <- dashboardPage(
  dashboardHeader(title = "test",
                  dropdownMenuOutput("menu")
  ),
  dashboardSidebar()
,
dashboardBody()
)

server <- function(input, output, session) {
  
  output$menu <- renderMenu({
    items <- if(Sys.Date()>as.Date("2022-06-30")){
      "June is over"
    }else(
      "June"
    )
    
    dropdownMenu(
      type = "notifications", 
      .list = items
    )
  })

}

shinyApp(ui, server)

Couldn't figure out how to fix it. Any help?

Answer 1

1. you can write if else in one line
2. to use .list argument, you need create your items in a list.
3. each item in the list needs to be notificationItem or messageItem. Read this: https://rstudio.github.io/shinydashboard/structure.html

Here is an example on how to fix:

library(shiny)
library(shinydashboard)

ui <- dashboardPage(
    dashboardHeader(title = "test",
                    dropdownMenuOutput("menu")
    ),
    dashboardSidebar()
    ,
    dashboardBody()
)

server <- function(input, output, session) {
    
    output$menu <- renderMenu({
        items <- list(
            notificationItem(if(Sys.Date()>as.Date("2022-06-30"))"June is over" else "June"),
            notificationItem("123")
        )
        dropdownMenu(
            type = "notifications", 
            .list = items
        )
    })
    
}

shinyApp(ui, server)