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###########################################################################/**
# @RdocDefault setGenericS3
#
# @title "Creates an S3 generic function"
#
# \description{
# \emph{Note that this method is a internal method called by
# @see "setMethodS3" and there is no reason for calling it directly!}\cr
#
# Creates a generic function in S3 style, i.e. setting a
# function with name \code{name} that dispatches the method \code{name}
# via \code{UseMethod}. If there is already a function named \code{name}
# that function is renamed to \code{name.default}.
# }
#
# @synopsis
#
# \arguments{
# \item{name}{The name of the generic function.}
# \item{export}{A @logical setting attribute \code{"export"}.}
# \item{envir}{The environment for where this method should be stored.}
# \item{dontWarn}{If a non-generic method with the same name is found it
# will be "renamed" to a default method. If that method is found in
# a package with a name that is \emph{not} found in \code{dontWarn}
# a warning will be produced, otherwise it will be renamed silently.}
# \item{validators}{An optional @list of @functions that can be used
# to assert that the generated generic function meets certain
# criteria.}
# \item{...}{Not used.}
# \item{overwrite}{If @TRUE an already existing generic function with
# the same name will be overwritten, otherwise not.}
# }
#
# @examples "../incl/setGenericS3.Rex"
#
# \seealso{
# To define a method for a class see @see "setMethodS3".
# For more information about S3, see @see "base::UseMethod".
# }
#
# @author
#
# @keyword programming
# @keyword methods
#*/###########################################################################
setGenericS3.default <- function(name, export=TRUE, envir=parent.frame(), dontWarn=getOption("dontWarnPkgs"), validators=getOption("R.methodsS3:validators:setGenericS3"), overwrite=FALSE, ...) {
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Validate arguments
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Argument 'name':
if (nchar(name) == 0L) {
stop("Cannot set S3 generic method. Argument 'name' is empty.")
}
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Backward compatibility tests
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
args <- list(...)
if (is.element("enforceRCC", names(args))) {
.Defunct(msg = "Argument 'enforceRCC' of setGenericS3() has been replaced by argument 'validators'.")
}
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 0. Define local constants and local functions
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 'get' is illegal, because if it is redefined in a package, library() will
# maybe load and set the new get, which is then a generic function, and the
# next thing it will try to get() (it uses get internally) will not be
# retrieved, since get.default() might not be loaded at this time, but later.
PROTECTED.NAMES <- c("get")
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 1. Test the definition using validators
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
if (!is.null(validators)) {
for (validator in validators) {
validator(name=name, envir=envir, dontWarn=dontWarn, type="setGenericS3")
}
}
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 2. Check for forbidden names
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
if (is.element(name, R.KEYWORDS))
stop("Method names must not be same as a reserved keyword in R: ", name)
if (is.element(name, PROTECTED.NAMES))
stop("Trying to use an unsafe generic method name (trust us, it is for a *good* reason): ", name)
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 2. Find the environment where sys.source() loads the package, which is
# the local variable (argument) of sys.source() named as "envir".
# Unfortunately, the only way we can be sure which of the parent frames
# are the sys.source() function frame is to compare its definition with
# each of the definitions of the parent frames using sys.function().
# Comment: sys.source() is used by library() and require() for loading
# packages. Also note that packages that are currently loaded are not in
# the search path, cf. search(), and there and standard exists() will not
# find it. *Not* checking the currently loading environment would *not*
# be harmful, but it would produce too many warnings.
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
sys.source.def <- get("sys.source", mode="function", envir=baseenv())
loadenv <- NULL
for (framePos in sys.parents()[-1L]) {
if (identical(sys.source.def, sys.function(framePos))) {
loadenv <- parent.frame(framePos)
break
}
}
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 3. Check for preexisting functions with the same name
# i) in the environment that we are saving to ('envir'),
# ii) in the currently loading environment ('loadenv'), or
# iii) (optional) in the environments in the search path.
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
envirs <- c(envir, loadenv)
if (getOption("R.methodsS3:useSearchPath", TRUE)) {
envirs <- c(envirs, lapply(search(), FUN=as.environment))
}
inherits <- rep(FALSE, times=length(envirs))
checkImports <- getOption("R.methodsS3:checkImports:setGenericS3", FALSE)
if (checkImports) inherits[1:2] <- TRUE
fcn <- .findFunction(name, envir=envirs, inherits=inherits)
fcnDef <- fcn$fcn
fcnPkg <- fcn$pkg
if (!overwrite && !is.null(fcnDef)) {
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 4a. Is it already a generic function?
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
isGeneric <- isGenericS3(fcnDef) || isGenericS4(fcnDef)
# If it is a generic function, we are done!
if (isGeneric) {
# TO DO: Update generic functions with '...', if missing.
return()
}
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 4b. ... or, is there already a default function with the same name?
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Search for preexisting default function in the same environments as above.
nameDefault <- paste(name, ".default", sep="")
fcn <- .findFunction(nameDefault, envir=envirs, inherits=inherits)
defaultExists <- !is.null(fcn$fcn)
defaultPkg <- fcn$pkg
if (defaultExists) {
msg <- paste("Could not create generic function. There is already a non-generic function named ", name, "() in ", sQuote(fcnPkg), " with the same name as an existing default function ", nameDefault, "() in ", sQuote(defaultPkg), ".", sep = "")
action <- Sys.getenv("R_R_METHODSS3_SETGENERICS3_ONDEFAULTEXISTS", "error")
action <- getOption("R.methodsS3.setGenericS3.onDefaultExists", action)
if (identical(action, "error")) {
stop(msg)
} else {
warning(msg)
return()
}
}
## Assign 'S3class' attribute (an R.methodsS3 thing)
attr(fcnDef, "S3class") <- "default"
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# 4c. "Rename" the function to a default function
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
assign(nameDefault, substitute(fcn, list(fcn=fcnDef)), envir=envir)
if (!is.element(fcnPkg, dontWarn)) {
warning("Renamed the preexisting function ", name, " to ",
nameDefault, ", which was defined in environment ", fcnPkg, ".")
}
} # if (...)
# By default all generic functions have '...' arguments
argsStr <- "..."
# Should argument 'value' be added?
isReplacementFunction <- (regexpr("<-$", name) != -1L)
if (isReplacementFunction) {
argsStr <- paste(c(argsStr, "value"), collapse=", ")
}
# Create a generic function
src <- sprintf("...tmpfcn <- function(%s) UseMethod(\"%s\")", argsStr, name)
src <- c(src, sprintf("R.methodsS3:::export(...tmpfcn) <- %s", export))
src <- c(src, sprintf("\"%s\" <- ...tmpfcn", name))
src <- c(src, "rm(list=\"...tmpfcn\")")
src <- paste(src, collapse=";\n")
expr <- parse(text=src)
eval(expr, envir=envir)
} # setGenericS3.default()
S3class(setGenericS3.default) <- "default"
export(setGenericS3.default) <- FALSE
setGenericS3.default("setGenericS3") # Creates itself ;)
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