stabilize_chr: Ensure a character argument meets expectations

In stbl: Stabilize Function Arguments

Ensure a character argument meets expectations

Description

to_chr() checks whether an argument can be coerced to character without losing information, returning it silently if so. Otherwise an informative error message is signaled.

stabilize_chr() can check more details about the argument, but is slower than to_chr().

stabilize_chr_scalar() and to_chr_scalar() are optimized to check for length-1 character vectors.

Usage

stabilize_chr(
  x,
  ...,
  allow_null = TRUE,
  allow_na = TRUE,
  min_size = NULL,
  max_size = NULL,
  regex = NULL,
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

stabilize_chr_scalar(
  x,
  ...,
  allow_null = TRUE,
  allow_zero_length = TRUE,
  allow_na = TRUE,
  regex = NULL,
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

to_chr(
  x,
  ...,
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

## S3 method for class ''NULL''
to_chr(x, ..., allow_null = TRUE, x_arg = caller_arg(x), call = caller_env())

to_chr_scalar(
  x,
  ...,
  allow_null = TRUE,
  allow_zero_length = TRUE,
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

Arguments

x	The argument to stabilize.
...	Arguments passed to methods.
allow_null	⁠(length-1 logical)⁠ Is NULL an acceptable value?
allow_na	⁠(length-1 logical)⁠ Are NA values ok?
min_size	⁠(length-1 integer)⁠ The minimum size of the object. Object size will be tested using vctrs::vec_size().
max_size	⁠(length-1 integer)⁠ The maximum size of the object. Object size will be tested using vctrs::vec_size().
regex	⁠(character, list, or stringr_pattern)⁠ One or more optional regular expressions to test against the values of x. This can be a character vector, a list of character vectors, or a pattern object from the {stringr} package (e.g., stringr::fixed("a.b")). The default error message for non-matching values will include the pattern itself (see regex_must_match()). To provide a custom message, supply a named character vector where the value is the regex pattern and the name is the message that should be displayed. To check that a pattern is not matched, attach a negate attribute set to TRUE. If a complex regex pattern throws an error, try installing the stringi package.
x_arg	⁠(length-1 character)⁠ An argument name for x. The automatic value will work in most cases, or pass it through from higher-level functions to make error messages clearer in unexported functions.
call	(environment) The execution environment to mention as the source of error messages.
x_class	⁠(length-1 character)⁠ The class name of x to use in error messages. Use this if you remove a special class from x before checking its coercion, but want the error message to match the original class.
allow_zero_length	⁠(length-1 logical)⁠ Are zero-length vectors acceptable?

Details

These functions have two important differences from base::as.character():

• lists and data.frames are not coerced to character. In base R, such objects are coerced to character representations of their elements. For example, as.character(list(1:3)) returns "1:10". In the unlikely event that this is the expected behavior, use as.character() instead.

• NULL values can be rejected as part of the call to this function (with allow_null = FALSE).

Value

The argument as a character vector.

Examples

to_chr("a")
to_chr(letters)
to_chr(1:10)
to_chr(1 + 0i)
to_chr(NULL)
try(to_chr(NULL, allow_null = FALSE))

to_chr_scalar("a")
try(to_chr_scalar(letters))

stabilize_chr(letters)
stabilize_chr(1:10)
stabilize_chr(NULL)
try(stabilize_chr(NULL, allow_null = FALSE))
try(stabilize_chr(c("a", NA), allow_na = FALSE))
try(stabilize_chr(letters, min_size = 50))
try(stabilize_chr(letters, max_size = 20))
try(stabilize_chr(c("hide", "find", "find", "hide"), regex = "hide"))

stabilize_chr_scalar(TRUE)
stabilize_chr_scalar("TRUE")
try(stabilize_chr_scalar(c(TRUE, FALSE, TRUE)))
stabilize_chr_scalar(NULL)
try(stabilize_chr_scalar(NULL, allow_null = FALSE))

stbl documentation built on Nov. 5, 2025, 6:02 p.m.