assert_character_scalar: Is an Argument a Character Scalar (String)?
In epijim/admiral: ADaM in R Asset Library

Description Usage Arguments Value Author(s) Examples

Checks if an argument is a character scalar and (optionally) whether it matches one of the provided values.

assert_character_scalar(
  arg,
  values = NULL,
  case_sensitive = TRUE,
  optional = FALSE
)

`arg`	A function argument to be checked
`values`	A `character` vector of valid values for `arg`
`case_sensitive`	Should the argument be handled case-sensitive? If set to `FALSE`, the argument is converted to lower case for checking the permitted values and returning the argument.
`optional`	Is the checked parameter optional? If set to `FALSE` and `arg` is `NULL` then an error is thrown

The function throws an error if arg is not a character vector or if arg is a character vector but of length > 1 or if its value is not one of the values specified. Otherwise, the input is returned invisibly.

Thomas Neitmann

example_fun <- function(msg_type) {
  assert_character_scalar(msg_type, values = c("warning", "error"))
}

example_fun("warning")

try(example_fun("message"))

try(example_fun(TRUE))

# handling parameters case-insensitive
example_fun2 <- function(msg_type) {
  msg_type <- assert_character_scalar(msg_type,
                                      values = c("warning", "error"),
                                      case_sensitive = FALSE)
 if (msg_type == "warning") {
   print("A warning was requested.")
 }
}

example_fun2("Warning")