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Send input validation messages to output

Source: R/validate_inputs.R
validate_inputs.Rd

Captures messages from InputValidator objects and collates them into one message passed to validate.

Usage 

validate_inputs(..., header = "Some inputs require attention")

Arguments

...

either any number of InputValidator objects or an optionally named, possibly nested list of InputValidator objects, see Details

header

(character(1)) generic validation message; set to NULL to omit

Value

Returns NULL if the final validation call passes and a shiny.silent.error if it fails.

Details

shiny::validate is used to withhold rendering of an output element until certain conditions are met and to print a validation message in place of the output element. shinyvalidate::InputValidator allows to validate input elements and to display specific messages in their respective input widgets. validate_inputs provides a hybrid solution. Given an InputValidator object, messages corresponding to inputs that fail validation are extracted and placed in one validation message that is passed to a validate/need call. This way the input validator messages are repeated in the output.

The ... argument accepts any number of InputValidator objects or a nested list of such objects. If validators are passed directly, all their messages are printed together under one (optional) header message specified by header. If a list is passed, messages are grouped by validator. The list's names are used as headers for their respective message groups. If neither of the nested list elements is named, a header message is taken from header.

See also

shinyvalidate::InputValidator, shiny::validate

Examples 

library(shiny)
library(shinyvalidate)

ui <- fluidPage(
  selectInput("method", "validation method", c("sequential", "combined", "grouped")),
  sidebarLayout(
    sidebarPanel(
      selectInput("letter", "select a letter:", c(letters[1:3], LETTERS[4:6])),
      selectInput("number", "select a number:", 1:6),
      br(),
      selectInput("color", "select a color:",
        c("black", "indianred2", "springgreen2", "cornflowerblue"),
        multiple = TRUE
      ),
      sliderInput("size", "select point size:",
        min = 0.1, max = 4, value = 0.25
      )
    ),
    mainPanel(plotOutput("plot"))
  )
)

server <- function(input, output) {
  # set up input validation
  iv <- InputValidator$new()
  iv$add_rule("letter", sv_in_set(LETTERS, "choose a capital letter"))
  iv$add_rule("number", function(x) {
    if (as.integer(x) %% 2L == 1L) "choose an even number"
  })
  iv$enable()
  # more input validation
  iv_par <- InputValidator$new()
  iv_par$add_rule("color", sv_required(message = "choose a color"))
  iv_par$add_rule("color", function(x) {
    if (length(x) > 1L) "choose only one color"
  })
  iv_par$add_rule(
    "size",
    sv_between(
      left = 0.5, right = 3,
      message_fmt = "choose a value between {left} and {right}"
    )
  )
  iv_par$enable()

  output$plot <- renderPlot({
    # validate output
    switch(input[["method"]],
      "sequential" = {
        validate_inputs(iv)
        validate_inputs(iv_par, header = "Set proper graphical parameters")
      },
      "combined" = validate_inputs(iv, iv_par),
      "grouped" = validate_inputs(list(
        "Some inputs require attention" = iv,
        "Set proper graphical parameters" = iv_par
      ))
    )

    plot(faithful$eruptions ~ faithful$waiting,
      las = 1, pch = 16,
      col = input[["color"]], cex = input[["size"]]
    )
  })
}

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