Non-standard set-functions in R Reference Classes

I don't think you can do this with your desired syntax.

Note that you will get the same error if you run any assignment like that, e.g.

a_person$hello("first") <- "John"

so it's really a basic problem.

What does work, is the following syntax:

name(a_person, "first") <- "John"

Altogether you could then have something like below:

PersonRCGen <- setRefClass("Person",
                  fields = list(
                    fullname = "list",
                    gender = "character"
                  ),
                  methods = list(
                    initialize = function(...) {
                      initFields(...)
                    },
                    name = function(x) {
                      .self$fullname[[x]]
                    }
                  )
)

setGeneric("name<-", function(x, y, value) standardGeneric("name<-"))
setMethod("name<-", sig = "ANY", function(x, y, value) {
  UseMethod("name<-")
})
# some extras
"name<-.default" <- function(x, y, value) {
  stop(paste("name assignment (name<-) method not defined for class", class(x)))
}
"name<-.list" <- function(x, y, value) {
  x[[y]] <- value
  return(x)
}
# and here specifically
"name<-.Person" <- function(x, y, value) {
  x$fullname[[y]] <- value
  return(x)
}

# example to make use of the above
a_person <- PersonRCGen$new(
  fullname = list(
    first = "Jane",
    last = "Doe"
  ),
  gender = "F"
)

a_person$name("first")
#> [1] "Jane"
name(a_person, "middle") <- "X."
a_person$name("middle")
#> [1] "X."

I'm aware this is not exactly what you want but I hope it helps.

I am probably misunderstanding what you are trying to achieve but what's wrong with this?

person = setRefClass("Person",
                     fields = list(
                       fullname = "list",
                       gender = "character"
                     ))

a_person = person$new(fullname = list(first = "James", last = "Brown"), gender="M")

a_person$fullname$first = "Bob"

a_person

Reference class object of class "Person"
Field "fullname":
$`first`
[1] "Bob"

$last
[1] "Brown"

Field "gender":
[1] "M"