Class for applicational settings — Settings • R.utils

Package: R.utils
Class Settings

Object
~~|
~~+--Options
~~~~~~~|
~~~~~~~+--Settings

Directly known subclasses:

public static class Settings
extends Options

Class for applicational settings.

Settings(basename=NULL, ...)

Arguments

basename: A character string of the basename of the settings file.
...: Arguments passed to constructor of superclass Options.

Fields and Methods

Methods:

	`findSettings`	-
	`getLoadedPathname`	-
	`isModified`	-
	`loadAnywhere`	-
	`promptAndSave`	-
	`saveAnywhere`	-

Methods inherited from Options:
as.character, as.list, equals, getLeaves, getOption, hasOption, names, nbrOfOptions, setOption, str

Methods inherited from Object:
$, $<-, [[, [[<-, as.character, attach, attachLocally, clearCache, clearLookupCache, clone, detach, equals, extend, finalize, getEnvironment, getFieldModifier, getFieldModifiers, getFields, getInstantiationTime, getStaticInstance, hasField, hashCode, ll, load, names, objectSize, print, save

Load settings with package and save on exit

Here is a generic .First.lib() function for loading settings with package. It also (almost) assures that the package is detached when R finishes. See onSessionExit() why it is not guaranteed!

The almost generic .Last.lib() function, which will prompt user to save settings, is called when a package is detached.

It is custom to put these functions in a file named zzz.R.

.First.lib():


  .First.lib <- function(libname, pkgname) {
    # Write a welcome message when package is loaded
    pkg <- Package(pkgname)
    assign(pkgname, pkg, pos=getPosition(pkg))

    # Read settings file ".<pkgname>Settings" and store it in package
    # variable '<pkgname>Settings'.
    varname <- paste(pkgname, "Settings")
    basename <- paste(".", varname, sep="")
    settings <- Settings$loadAnywhere(basename, verbose=TRUE)
    if (is.null(settings))
      settings <- Settings(basename)
    assign(varname, settings, pos=getPosition(pkg))

    # Detach package when R finishes, which will save package settings too.
    onSessionExit(function(...) detachPackage(pkgname))

    packageStartupMessage(getName(pkg), " v", getVersion(pkg),
        " (", getDate(pkg), ") successfully loaded. See ?", pkgname,
        " for help.\n", sep="")
  } # .First.lib()

.Last.lib():


  .Last.lib <- function(libpath) {
    pkgname <- "<package name>"

    # Prompt and save package settings when package is detached.
    varname <- paste(pkgname, "Settings", sep="")
    if (exists(varname)) {
      settings <- get(varname)
      if (inherits(settings, "Settings"))
        promptAndSave(settings)
    }
  } # .Last.lib()

Author

Henrik Bengtsson

Examples

# Load settings from file, or create default settings
basename <- "some.settings"
settings <- Settings$loadAnywhere(basename)
if (is.null(settings))
  settings <- Settings(basename)

# Set default options, if missing.
setOption(settings, "graphics/verbose", TRUE, overwrite=FALSE)
setOption(settings, "io/verbose", Verbose(threshold=-1), overwrite=FALSE)

# Save and reload settings
path <- tempdir()
saveAnywhere(settings, path=path)
settings2 <- Settings$loadAnywhere(basename, paths=path)

# Clean up
file.remove(getLoadedPathname(settings2))
#> [1] TRUE

# Assert correctness
stopifnot(equals(settings, settings2))