assert_character_scalar {admiraldev}

Is an Argument a Character Scalar (String)?

Description

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

Usage

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

Arguments

arg

A function argument to be checked

values

A character vector of valid values for arg. Values is converted to a lower case vector if case_sensitive = FALSE is used.

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 argument optional? If set to FALSE and arg is NULL then an error is thrown

Value

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.

See Also

Checks for valid input and returns warning or errors messages: assert_atomic_vector(), assert_character_vector(), assert_data_frame(), assert_date_vector(), assert_expr_list(), assert_expr(), assert_filter_cond(), assert_function(), assert_integer_scalar(), assert_list_element(), assert_list_of(), assert_logical_scalar(), assert_named(), assert_numeric_vector(), assert_one_to_one(), assert_param_does_not_exist(), assert_s3_class(), assert_same_type(), assert_symbol(), assert_unit(), assert_vars(), assert_varval_list()

Examples

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 arguments 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")