Show only one notification in Shiny - r

Question

I would like to control the phone number by showing a notification :
If the user type a wrong number (like "aaaa")
If the user type a long number (greater than 10 digits)
I used the function showNotification from shiny with closeButton = FALSE and duration = NULL.
When the user type a wrong number, the notification popped up but when he type a long number the the notification also popped up but the previous one does not disappear
I would like to show only one notification (wrong number or long number) but not the both at the same time. How can we do that ? Here's my apps :
library(shiny)
library(shinydashboard)
library(shinydashboardPlus)
############# UI ############
body <- dashboardBody(
tabItems(
tabItem(tabName = "tab1",
fluidRow(
tags$h1('my title'),
textInput("phone_number", "enter your phone number", value = ""),
actionButton("button", "go")
)
)
)
)
ui <- dashboardPage(
title = "Example",
options = list(sidebarExpandOnHover = TRUE),
header = dashboardHeader(disable = FALSE),
sidebar = dashboardSidebar(
minified = TRUE, collapsed = TRUE,
sidebarMenu(id="menu",
menuItem("first tab", tabName = "mytab", icon = icon("fas fa-acorn"),
menuSubItem('menu1',
tabName = 'tab1',
icon = icon('fas fa-hand-point-right'))
)
)
),
body
)
############# SERVER ############
server <- function(input, output) {
observeEvent(
input$button,
{
if(is.na(as.numeric(input$phone_number))) {
showNotification(type = "error",
duration = NULL,
closeButton = FALSE,
"wrong number")
} else if(nchar(input$phone_number)<10) {
showNotification(type = "error",
duration = NULL,
closeButton = FALSE,
"too long (10 digits required)")
}
}
)
}
############# RUN THE APP ############
shinyApp(ui = ui, server = server)
Some help would be appreciated

Answer 1

I would not use a notification here, because they will always be displayed for a fixed time duration and at a different position of the window, which might confuse the user. I would just render the message in using a textOutput:
library(shiny)
library(shinyjs)
ui <- fluidPage(
useShinyjs(),
textInput("phone_number", "phone number"),
textOutput("phone_notification")
)
server <- function(input, output, session) {
output$phone_notification <- renderText({
if(input$phone_number == "") {
"" # empty is ok
}
else if(is.na(as.numeric(input$phone_number))) {
"wrong number"
} else if (nchar(input$phone_number) > 10) {
"too long"
} else {
"" # correct number
}
})
}
shinyApp(ui, server)
You can also style the text e.g. to make it red:
ui <- fluidPage(
useShinyjs(),
textInput("phone_number", "phone number"),
tagAppendAttributes(
textOutput("phone_notification"),
style = "color:red"
)
)

Answer 2

I needed the solution OP asked. I found the following code snippet to work in my case:
removeNotification(id = "onlyOnce", session = getDefaultReactiveDomain())
showNotification("Show me once", id = "onlyOnce")
See also: https://search.r-project.org/CRAN/refmans/shiny/html/showNotification.html