R/load.R

In KWB-R/kwb.utils: General Utility Functions Developed at KWB

# .optionName_loaded -----------------------------------------------------------

.optionName_loaded <- "kwb.utils.loaded"

# isLoaded ---------------------------------------------------------------------

#' Has a Script Been Loaded (with source)?
#' 
#' Check whether a script has been loaded (with source) or not. The information 
#' is read from a list that stores a logical value (\code{TRUE} or \code{FALSE})
#' for each script name for which \code{\link{setLoaded}} has been called.
#' 
#' @param scriptName name of the script for which to get the "loaded" state
#' @seealso \code{\link{setLoaded}} (see example there)
#' @export
#' @examples 
#' # For an example see kwb.utils::setLoaded()...
#' 
#' # In fact, the information about loaded scripts is stored in the
#' # R option "kwb.utils.loaded":
#' setLoaded("myScript")
#' 
#' options("kwb.utils.loaded")[[1]]
#' 
isLoaded <- function(scriptName)
{
  loaded <- defaultIfNULL(getOption(.optionName_loaded), list())
  
  defaultIfNULL(loaded[[scriptName]], FALSE)
}

# setLoaded --------------------------------------------------------------------

#' Set the "loaded" Status for a Script
#' 
#' You may use this function at the last line of your script to indicate that 
#' this script has already been loaded. This information is stored in the R 
#' option "kwb.utils.loaded" from which you may read the information back with 
#' \code{\link{isLoaded}}.
#' 
#' @param scriptName name of the script for which we want to set the "loaded"
#'   state
#' @param isLoaded logical. Use \code{TRUE} to indicate that the script
#'   \code{scriptName} has been loaded and use \code{FALSE} to indicate that the
#'   script is not loaded (e.g. because you cleared the workspace in the
#'   meanwhile).
#' @seealso \code{\link{isLoaded}}
#' @export
#' @examples 
#' # If you have a script with the main part on top and the required functions
#' # defined below (as recommended by Robert C. Martin, the author of "Clean
#' # Code") your script may look like this:
#' 
#' # Main part -----
#' 
#' # Check if the script has already been loaded (i.e. if setLoaded() has been 
#' # called, see end of script). If yes, we can enter the main section. Otherwise
#' # we have to skip the main section since the function sayHello() is not yet
#' # defined.
#' if (isLoaded("welcome")) {
#'   sayHello(who = "Hauke")
#' }
#' 
#' # Functions -----
#' sayHello <- function(who) {
#'   clearConsole()
#'   cat("***\n***\n*** Hello", who, "how are you?\n***\n***\n")
#' }
#' 
#' # At the end of your script, call setLoaded() to indicate that your script is
#' # loaded now. If you "source" the script a second time, isLoaded("welcome") 
#' # will return TRUE and thus the main section will be entered...
#' setLoaded("welcome")
#' 
setLoaded <- function(scriptName, isLoaded = TRUE)
{
  stopifnot(is.logical(isLoaded) && length(isLoaded) == 1)
  
  # Get the R option (list of booleans)
  loaded <- defaultIfNULL(getOption(.optionName_loaded), list())
    
  # Update the list of booleans for the given script name
  loaded[[scriptName]] <- isLoaded
  
  # Set the R option
  do.call(options, args = structure(list(loaded), names = .optionName_loaded))
}