R/getNnnByName.R

In R.oo: R Object-Oriented Programming with or without References

.getFunctionByName <- function(name, where=c("ns", "search", "ns*"), envir=NULL, callEnvir=as.environment(-1L), class="function", mustExist=TRUE, ...) {
  # Backward compatibility (ignore where="ns*" if explicitly disabled)
  if (!getOption("R.oo::Class/searchNamespaces", TRUE)) {
    where <- setdiff(where, "ns*")
  }

  # Ignore where = "ns" if 'envir' was not specified
  if (is.null(envir)) {
    where <- setdiff(where, "ns")
  }

  # Search each 'where'...
  for (kk in seq_along(where)) {
    whereKK <- where[kk]

    # (a) Search a specific environment?
    #    (which should be a namespace of package)
    if (whereKK == "ns") {
      if (exists(name, mode="function", envir=envir, inherits=TRUE)) {
        res <- get(name, mode="function", envir=envir, inherits=TRUE)
        if (inherits(res, class)) return(res)
      }
    }

    # (b) Search globally?
    if (whereKK == "search") {
      envirT <- callEnvir
      if (exists(name, mode="function", envir=envirT, inherits=TRUE)) {
        res <- get(name, mode="function", envir=envirT, inherits=TRUE)
        if (inherits(res, class)) return(res)
      }
    }

    # (c) Search all loaded namespaces?
    if (whereKK == "ns*") {
      for (pkg in loadedNamespaces()) {
        envirT <- getNamespace(pkg)
        if (exists(name, mode="function", envir=envirT, inherits=TRUE)) {
          res <- get(name, mode="function", envir=envirT, inherits=TRUE)
          if (inherits(res, class)) return(res)
        }
      }
    }
  } # for (kk in ...)

  if (mustExist) {
    # Don't use throw() here, because it may result in an endless loop
    # if Exception is not found. /HB 2012-11-23
    stop(sprintf("INTERNAL ERROR: No such %s: %s", class, name))
  }

  # Not found
  NULL
} # .getFunctionByName()


.getS3Method <- function(name, ...) {
  .getFunctionByName(name, class="function", ..., callEnvir=as.environment(-1L))
}

.getClassByName <- function(name, ...) {
  .getFunctionByName(name, class="Class", ..., callEnvir=as.environment(-1L))
}