R/validator.R

In shinyreforms: Add Forms to your 'Shiny' App

#' Class representing a Validator.
#'
#' @description
#' Validators are used to validate input fields in a ShinyForm.
#' Validators are to be used with the validatedInput function.
#' A single input field can have several validators.
#'
#' @examples
#' if(interactive()){
#' Validator(function(value) {
#'   ...
#' }, "Validation failed!")
#' }
#'
#' @field test Function returning a boolean value which will be used
#'   to validate input.
#' @field failMessage Error message to display when validation fails.
#'
#' @details
#' Package shinyreformss defines a set of commonly used pre-defined
#' Validators. These include:
#' \describe{
#'  \item{ValidatorMinLength(minLength):}{Will fail if string is shorter than minLength.}
#'  \item{ValidatorMaxLength(maxLength):}{Will fail if string is longer than maxLength.}
#'  \item{ValidatorNonEmpty():}{Will fail if string is empty.}
#' }
#'
#' @importFrom R6 R6Class
#' @export
Validator <- R6Class(
  "Validator",
  public = list(
    test = NULL,
    failMessage = "",

    #' @description
    #' Creates a Validator object.
    #'
    #' @param test A function to test the input. Should
    #'  take a single value as input and return a boolean.
    #' @param failMessage A fail message to be displayed.
    initialize = function(test, failMessage) {
      # Wrap the test function up to check for emptyness first
      self$test <- function(value) {
        if (is.null(value)) {
          return(FALSE)
        }
        if (length(value) == 0) {
          return(FALSE)
        }

        return(test(value))
      }

      self$failMessage <- failMessage
    },

    #' @description
    #' Performs a check on the input.
    #'
    #' @param value Input value to be tested.
    #' @return TRUE if the check passes, FALSE if otherwise.
    check = function(value) {
      return(self$test(value))
    }
  )
)