Convert labels<- to S4 generic function

NEWS.md

@@ -42,6 +42,7 @@
 * Dataset `faux_cell` and function `generate_faux_cell()` replace `chondro` dataset (cbeleites/hyperSpec#125, cbeleites/hyperSpec#156, cbeleites/hyperSpec#180, cbeleites/hyperSpec#229).
 * Documentation aliases have been updated. Now, ?hyperSpec points to the function `hyperSpec()`, and to refer to the package, `package?hyperSpec` should be used (#129).
 * Vignette `hyperSpec.Rmd`: suggested packages (`pls`) are now loaded conditionally so the vignette builds even when they are not installed.
+* Function `labels<-()` converted into an S4 generic, making it consistent with the existing `labels()` S4 generic (r-hyperspec/hyperSpec#115).
 
 
 ### Bugfixes

R/labels.R

@@ -140,7 +140,8 @@ hySpc.testthat::test(.labels) <- function() {
 #' @examples
 #'
 #' labels(flu, "c") <- expression("/"("c", "mg / l"))
-`labels<-` <- function(object, which = NULL, ..., value) {
+# helper function (similar to .labels for the getter)
+.labels_replace <- function(object, which = NULL, ..., value) {
   assert_hyperSpec(object)
   validObject(object)
 
@@ -163,6 +164,17 @@ hySpc.testthat::test(.labels) <- function() {
   object
 }
 
+# generic replacement function
+#' @export
+setGeneric("labels<-", function(object, which = NULL, ..., value) {
+  standardGeneric("labels<-")
+})
+
+setMethod("labels<-", 
+  signature = signature(object = "hyperSpec"), 
+  .labels_replace
+)
+
 
 # Unit tests -----------------------------------------------------------------