% Generated by roxygen2 (4.0.0): do not edit by hand
\name{validateInput}
\alias{validateInput}
\title{Check if input values satisfy the output rendering function}
\usage{
validateInput(...)
}
\arguments{
\item{...}{A list of arguments, and each argument takes either a logical
value or a list of length 2. When an argument takes a logical value, the
value is the condition on which the rendering function should stop (the
condition normally returns \code{TRUE} or \code{FALSE}, and this function
stops when the condition is \code{FALSE}; see Details). When the argument
is a list, the first element of the list is an error message (a character
vector), and the second element is the condition explained before.}
}
\description{
For an output rendering function (e.g. \code{\link{renderPlot}()}), we may
need to check certain input values before we can render the output. If the
input values do not satisfy the rendering function, we can signal an error to
indicate this special situation.
}
\details{
For the sake of convenience, it is not strictly required that the condition
is a logical value, and we can use input values themselves as the testing
conditions, since there are a few common cases in which the input values are
often considered invalid, including \code{NULL}, \code{NA}, values of length
zero, and a special case for action buttons when they take values of 0 (i.e.
not clicked). If any of these values happen to be valid, you can explicitly
turn them to logical values. For example, if we allow \code{NA} but not
\code{NULL}, we can use the condition \code{!is.null(input$foo)}, because
\code{!is.null(NA) == TRUE}.
}
\examples{
# in ui.R
fluidPage(
  actionButton('in1', 'Go!'),
  checkboxGroupInput('in2', 'Check some letters', choices = head(LETTERS)),
  selectizeInput('in3', 'Select a state', choices = state.name),
  plotOutput('plot')
)

# in server.R
function(input, output) {
  output$plot <- renderPlot({
    validateInput(
      input$in1,  # ensure the button has been clicked
      list('Check at least one letter!', input$in2),
      list('Please choose a state.', input$in3 == '')
    )
    plot(1:10, main = paste(c(input$bar, input$foo), collapse = ', '))
  })
}
}