An example of subclassing conditions and then handling conditions of only a particular class.

gistfile1.txt

# constructor based on the simpleError function
my_error = function(message, call = NULL){
  class = c("my_error", "error", "condition")
  structure(
    list(as.character(message), call = call),
    class = class
    )
  }

# my_error still needs to be signaled with stop():
my_error("this is an object of class \"my_error\", subclass of \"error\") |> stop()

# now it can be specifically handled in tryCatch or withCallingHandlers
tryCatch(
  # expression
  my_error("some message") |> stop(),
  # we handle these conditions
  my_error = functon(e){ paste0("We caught error of class \"my_error\" with message: ", conditionMessage(e) }
  )