R/predicates.R

In result: Result Type for Safely Handling Operations that can Succeed or Fail

#' Checks if an object is of \code{result} class
#'
#' @param obj object to check
#' @return \code{TRUE} if object is of \code{result} class,
#'    \code{FALSE} otherwise
#' @examples
#' is_result(success())
#' is_result(failure())
#' is_result(42)
#' @export
is_result <- function(obj) inherits(obj, "result")

#' Checks if an object is of \code{success} class
#'
#' @param obj object to check
#' @return \code{TRUE} if object is of \code{success} class,
#'    \code{FALSE} otherwise
#' @examples
#' is_success(success())
#' is_success(failure())
#' @export
is_success <- function(obj) UseMethod("is_success", obj)

#' Checks if an object is of \code{failure} class
#'
#' @param obj object to check
#' @return \code{TRUE} if object is of \code{failure} class,
#'    \code{FALSE} otherwise
#' @examples
#' is_failure(success())
#' is_failure(failure())
#' @export
is_failure <- function(obj) UseMethod("is_failure", obj)

#' @method is_success success
#' @export
is_success.success <- function(obj) TRUE

#' @method is_success failure
#' @export
is_success.failure <- function(obj) FALSE

#' @method is_failure result
#' @export
is_failure.result <- function(obj) !is_success(obj)