R: Check if an argument is a string

checkString {checkmate} | R Documentation

## Check if an argument is a string

### Description

A string is defined as a scalar character vector.

### Usage

    checkString(x, na.ok = FALSE, min.chars = NULL, pattern = NULL,
      fixed = NULL, ignore.case = FALSE, null.ok = FALSE)

    check_string(x, na.ok = FALSE, min.chars = NULL, pattern = NULL,
      fixed = NULL, ignore.case = FALSE, null.ok = FALSE)

    assertString(x, na.ok = FALSE, min.chars = NULL, pattern = NULL,
      fixed = NULL, ignore.case = FALSE, null.ok = FALSE,
      .var.name = vname(x), add = NULL)

    assert_string(x, na.ok = FALSE, min.chars = NULL, pattern = NULL,
      fixed = NULL, ignore.case = FALSE, null.ok = FALSE,
      .var.name = vname(x), add = NULL)

    testString(x, na.ok = FALSE, min.chars = NULL, pattern = NULL,
      fixed = NULL, ignore.case = FALSE, null.ok = FALSE)

    test_string(x, na.ok = FALSE, min.chars = NULL, pattern = NULL,
      fixed = NULL, ignore.case = FALSE, null.ok = FALSE)

    expect_string(x, na.ok = FALSE, min.chars = NULL, pattern = NULL,
      fixed = NULL, ignore.case = FALSE, null.ok = FALSE, info = NULL,
      label = vname(x))

### Arguments

`x` | [any] Object to check.
`na.ok` | [`logical(1)`] Are missing values allowed? Default is `FALSE`.
`min.chars` | [`integer(1)`] Minimum number of characters in each element of `x`.
`pattern` | [`character(1L)`] Regular expression as used in `grepl`. All elements of `x` must comply to this pattern.
`fixed` | [`character(1)`] Substring to detect in `x`. Will be used as `pattern` in `grepl` with option `fixed` set to `TRUE`. All elements of `x` must contain this substring.
`ignore.case` | [`logical(1)`] See `grepl`. Default is `FALSE`.
`null.ok` | [`logical(1)`] If set to `TRUE`, `x` may also be `NULL`. In this case only a type check of `x` is performed, all additional checks are disabled.
`.var.name` | [`character(1)`] Name of the checked object to print in assertions. Defaults to the heuristic implemented in `vname`.
`add` | [`AssertCollection`] Collection to store assertion messages. See `AssertCollection`.
`info` | [character(1)] Extra information to be included in the message for the testthat reporter. See `expect_that`.
`label` | [`character(1)`] Name of the checked object to print in messages. Defaults to the heuristic implemented in `vname`.

### Details

This function does not distinguish between `NA`, `NA_integer_`, `NA_real_`, `NA_complex_` `NA_character_` and `NaN`.

### Value

Depending on the function prefix: If the check is successful, the functions `assertString`/`assert_string` return `x` invisibly, whereas `checkString`/`check_string` and `testString`/`test_string` return `TRUE`. If the check is not successful, `assertString`/`assert_string` throws an error message, `testString`/`test_string` returns `FALSE`, and `checkString` returns a string with the error message. The function `expect_string` always returns an `expectation`.

### See Also

Other scalars: `checkCount`, `checkFlag`, `checkInt`, `checkNumber`, `checkScalarNA`, `checkScalar`

### Examples

    testString("a")
    testString(letters)

[Package checkmate version 1.8.2 Index]