I'm new to R and I'm currently trying to supply the enumeration-like argument to the R function (or the RC/R6 class method), I currently use character vector plus match.arg similar to the following:

EnumTest = function(enum = c("BLUE", "RED", "BLACK")) {
  enumArg <-
    switch(
      match.arg(enum), "BLUE" = 0L, "RED" = 1L, "BLACK" = 2L
    )
  switch(enumArg,
         # do something
  )
}

Is there are better/more concise way to imitate enum-like behavior in R? E.g. one big problem that user has to know the set of possible values for the argument and manually type it as a string - without any suggestion or auto-completion...

If there is no other better way, one thing that could improve above approach - it'd be nice to make it more concise by say predefining enums globally or say as private members of R6 class:

Color <- c("BLUE", "RED", "BLACK")

Then one could (re)use it in one or more function definitions, e.g.:

EnumTest = function(enum = Color) { 
...

However, I'm not sure how to use this Color vector in match.arg function. It'd be nice if I could define Color as a map with keys being actual color values and values being integer representation - but I'm not sure how sensible that is.. Anyways, maybe there are more common neat approaches exist.

The main goal would be to provide an easy-to-use intuitive interface to the user of my package and functions (e.g. easy way to find the set of possible values, tab-completion, auto-suggestion, etc..), followed by standardized development of such functions using enum-like arguments