validate_input: Validate input

In teal: Exploratory Web Apps for Analyzing Clinical Trials Data

Validate input

Description

Validate a Shiny input and send validation messages to the client. The message appears both in the input widget and in the output element that calls validate_input.

Usage

validate_input(
  inputId,
  condition = function(x) TRUE,
  message = "Check the input",
  session = shiny::getDefaultReactiveDomain()
)

need_input(
  inputId,
  condition = function(x) TRUE,
  message = "Check the input",
  session = shiny::getDefaultReactiveDomain()
)

use_validate_input_js()

Arguments

inputId	(character) Character of input ID(s) to validate
condition	(logical(1), ⁠function(x)⁠) Logical value or function returning logical value. Condition should determine expected state, FALSE throws.
message	(character(1)) Character string of validation message to display.
session	Shiny session object

Details

• ⁠validate_input():⁠

  Validate a Shiny input and send validation messages to the client. The message appears both in the input widget and in the output element that calls validate_input.

• need_input(): Validate a Shiny input and returns a message to be used in a shiny::validate() call. The message is sent to the client and appears both in the input widget. To observe the message in the output element, need_input() should be called inside a shiny::validate() call, e.g. via validate(validate_input(...)).

• use_validate_input_js():

  Include JavaScript for client-side input validation.

Value

NULL or shiny.silent.error when condition is not met

Examples

# Only run examples in interactive R sessions
options(device.ask.default = FALSE)

ui <- fluidPage(
  checkboxGroupInput("in1", "Check some letters", choices = head(LETTERS)),
  selectizeInput("in2", "Select a state", choices = c("", state.name)),
  use_validate_input_js(),
  plotOutput("plot")
)

server <- function(input, output) {
  output$plot <- renderPlot({
    validate_input("in1", condition = function(x) length(x) > 0, "Check at least one letter!")
    validate_input("in2", condition = function(x) x != "", "Please choose a state.")
    plot(1:10, main = paste(c(input$in1, input$in2), collapse = ", "))
  })
}

if (interactive()) {
  shinyApp(ui, server)
}

my_module <- module(
  label = "My Module",
  datanames = NULL,
  ui = function(id) {
    ns <- NS(id)
    tagList(
      checkboxGroupInput(ns("letters"), "Select letters:", choices = head(LETTERS), inline = TRUE),
      checkboxGroupInput(ns("letters2"), "Select letters:", choices = head(LETTERS), inline = TRUE),
      tags$h3("Sample plot"),
      plotOutput(ns("plot"))
    )
  },
  server = function(id, data) {
    moduleServer(id, function(input, output, session) {
      output$plot <- renderPlot({
        validate_input(
          "letters",
          condition = function(x) length(x) > 0,
          message = "Select at least one letter."
        )
        validate_input(
          c("letters", "letters2"),
          condition = function(x, y) all(!x %in% y),
          message = "Letters in the first group should not be in the second group."
        )
        tab <- rbind(
          Group1 = as.integer(head(LETTERS) %in% input$letters),
          Group2 = as.integer(head(LETTERS) %in% input$letters2)
        )
        colnames(tab) <- head(LETTERS)
        barplot(
          tab,
          beside = TRUE, legend.text = TRUE, main = "Selected letters per group",
          col = c("steelblue", "tomato")
        )
      })
    })
  }
)

app <- init(
  data = within(teal_data(), iris <- iris),
  modules = my_module
)

if (interactive()) {
  shinyApp(app$ui, app$server)
}
my_module <- module(
  label = "My Module",
  datanames = NULL,
  ui = function(id) {
    ns <- NS(id)
    tagList(
      checkboxGroupInput(ns("letters1"), "Select letters:", choices = head(LETTERS), inline = TRUE),
      checkboxGroupInput(ns("letters2"), "Select letters:", choices = head(LETTERS), inline = TRUE),
      tags$h3("Sample plot"),
      plotOutput(ns("plot"))
    )
  },
  server = function(id, data) {
    moduleServer(id, function(input, output, session) {
      output$plot <- renderPlot({
        validate(
          need_input(
            "letters1",
            condition = function(x) length(x) > 0,
            message = "Select at least one letter."
          ),
          need_input(
            c("letters1", "letters2"),
            condition = function(x, y) all(!x %in% y),
            message = "Letters in the first group should not be in the second group."
          )
        )
        tab <- rbind(
          Group1 = as.integer(head(LETTERS) %in% input$letters1),
          Group2 = as.integer(head(LETTERS) %in% input$letters2)
        )
        colnames(tab) <- head(LETTERS)
        barplot(
          tab,
          beside = TRUE, legend.text = TRUE, main = "Selected letters per group",
          col = c("steelblue", "tomato")
        )
      })
    })
  }
)

app <- init(
  data = within(teal_data(), iris <- iris),
  modules = my_module
)

if (interactive()) {
  shinyApp(app$ui, app$server)
}

teal documentation built on June 30, 2026, 5:11 p.m.