Skip to contents

Ensure a character argument meets expectations

Source: R/stabilize_chr.R, R/to_chr.R
stabilize_chr.Rd

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?

Value

The argument as a character vector.

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).

Examples

to_chr("a")
#> [1] "a"
to_chr(letters)
#>  [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"
#> [20] "t" "u" "v" "w" "x" "y" "z"
to_chr(1:10)
#>  [1] "1"  "2"  "3"  "4"  "5"  "6"  "7"  "8"  "9"  "10"
to_chr(1 + 0i)
#> [1] "1+0i"
to_chr(NULL)
#> NULL
try(to_chr(NULL, allow_null = FALSE))
#> Error in eval(expr, envir) : `NULL` must not be <NULL>.

to_chr_scalar("a")
#> [1] "a"
try(to_chr_scalar(letters))
#> Error in eval(expr, envir) : 
#>   `letters` must be a single <character>.
#> ✖ `letters` has 26 values.

stabilize_chr(letters)
#>  [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"
#> [20] "t" "u" "v" "w" "x" "y" "z"
stabilize_chr(1:10)
#>  [1] "1"  "2"  "3"  "4"  "5"  "6"  "7"  "8"  "9"  "10"
stabilize_chr(NULL)
#> NULL
try(stabilize_chr(NULL, allow_null = FALSE))
#> Error in eval(expr, envir) : `NULL` must not be <NULL>.
try(stabilize_chr(c("a", NA), allow_na = FALSE))
#> Error in eval(expr, envir) : 
#>   `c("a", NA)` must not contain NA values.
#> • NA locations: 2
try(stabilize_chr(letters, min_size = 50))
#> Error in eval(expr, envir) : `letters` must have size >= 50.
#> ✖ 26 is too small.
try(stabilize_chr(letters, max_size = 20))
#> Error in eval(expr, envir) : `letters` must have size <= 20.
#> ✖ 26 is too big.
try(stabilize_chr(c("hide", "find", "find", "hide"), regex = "hide"))
#> Error in eval(expr, envir) : 
#>   `c("hide", "find", "find", "hide")` must match the regex pattern "hide"
#> ✖ Some values fail the check.
#> • Locations: 2 and 3
#> • Values: find and find

stabilize_chr_scalar(TRUE)
#> [1] "TRUE"
stabilize_chr_scalar("TRUE")
#> [1] "TRUE"
try(stabilize_chr_scalar(c(TRUE, FALSE, TRUE)))
#> Error in eval(expr, envir) : 
#>   `c(TRUE, FALSE, TRUE)` must be a single <character>.
#> ✖ `c(TRUE, FALSE, TRUE)` has 3 values.
stabilize_chr_scalar(NULL)
#> NULL
try(stabilize_chr_scalar(NULL, allow_null = FALSE))
#> Error in eval(expr, envir) : `NULL` must not be <NULL>.