Strings - Validity

The constraints of a String value. Length counts characters as Kotlin does (String.length), and the byte rules count the bytes of an encoding, UTF-8 by default. The rules that compare with text you give take ignoreCase, false by default.

A null argument checks nothing. A rule that reads a value that may be missing, such as max(customer.limit), never fails because of it: required on that value reports it once.

MemberProfile.kt

data class MemberProfile(
    val handle: String?,
    val displayName: String?,
    val password: String?,
    val bio: String? = null
) : Validatable {
    override fun validation() = validation {
        ::handle required {
            lengthBetween(min = 3, max = 30)
            lowercase()
            slug()
        }
        ::displayName required {
            notBlank()
            trimmed()
        }
        ::password required {
            minLength(12)
            containsUppercase()
            containsDigit()
            containsSymbol()
        }
        ::bio ifPresent { maxBytes(500) }
    }
}

Constraint	Checks
`minLength`	Has at least `min` characters.
`maxLength`	Has at most `max` characters.
`length`	Has exactly `length` characters.
`lengthBetween`	Has between `min` and `max` characters, both included.
`minBytes`	Takes at least `min` bytes when encoded with `charset`.
`maxBytes`	Takes at most `max` bytes when encoded with `charset`.
`notEmpty`	Has at least one character.
`empty`	Has no characters.
`notBlank`	Has at least one character that is not whitespace.
`blank`	Is empty or has only whitespace.
`trimmed`	Does not start or end with whitespace.
`equalTo`	Is equal to `other`, ignoring case when `ignoreCase` is `true`.
`oneOf`	Is one of `values`, ignoring case when `ignoreCase` is `true`.
`enum`	Is the name of an entry of the enum `E`.
`contains`	Contains `text`.
`notContains`	Does not contain `text`.
`startsWith`	Starts with `prefix`.
`notStartsWith`	Does not start with `prefix`.
`endsWith`	Ends with `suffix`.
`notEndsWith`	Does not end with `suffix`.
`matches`	Of the string matches `regex`.
`notMatches`	Of the string does not match `regex`.
`uppercase`	Has no lowercase letters.
`lowercase`	Has no uppercase letters.
`letters`	Is not empty and has only letters, in any script.
`digits`	Is not empty and has only the digits `0` to `9`.
`lettersOrDigits`	Is not empty and has only letters, in any script, and the digits `0` to `9`.
`ascii`	Is not empty and has only ASCII characters.
`containsOnly`	Is not empty and has only characters from `characters`.
`containsUppercase`	Has at least one uppercase letter.
`containsLowercase`	Has at least one lowercase letter.
`containsDigit`	Has at least one of the digits `0` to `9`.
`containsSymbol`	Has at least one character that is not a letter, a digit or whitespace.
`normalized`	Is already in the Unicode normalization `form`.
`numeric`	Is a decimal number, such as `42`, `-7` or `+3.14`.
`integer`	Is a whole number, such as `42`, `-7` or `+3`.
`boolean`	Is `true` or `false`, in lowercase.

Length and bytes

`minLength`

minLength(min) on String Checks that the string has at least min characters. minLength

`maxLength`

maxLength(max) on String Checks that the string has at most max characters. maxLength

`length`

length(length) on String Checks that the string has exactly length characters. length

`lengthBetween`

lengthBetween(min, max) on String Checks that the string has between min and max characters, both included. lengthBetween

`minBytes`

minBytes(min, charset) on String Checks that the string takes at least min bytes when encoded with charset. minBytes

`maxBytes`

maxBytes(max, charset) on String Checks that the string takes at most max bytes when encoded with charset. Use it for columns and protocols that limit bytes, not characters: "é" is one character and two UTF-8 bytes. maxBytes

Empty and blank

`notEmpty`

notEmpty() on String Checks that the string has at least one character. A string of spaces passes. Use notBlank to refuse it. notEmpty

`empty`

empty() on String Checks that the string has no characters. empty

`notBlank`

notBlank() on String Checks that the string has at least one character that is not whitespace. notBlank

`blank`

blank() on String Checks that the string is empty or has only whitespace. blank

`trimmed`

trimmed() on String Checks that the string does not start or end with whitespace. trimmed

Comparing with text

`equalTo`

equalTo(other, ignoreCase) on String Checks that the string is equal to other, ignoring case when ignoreCase is true. equalTo

`oneOf`

oneOf(values, ignoreCase) on String Checks that the string is one of values, ignoring case when ignoreCase is true. oneOf

`enum`

enum<E>(ignoreCase) on String Checks that the string is the name of an entry of the enum E. enum

`contains`

contains(text, ignoreCase) on String Checks that the string contains text. contains

`notContains`

notContains(text, ignoreCase) on String Checks that the string does not contain text. notContains

`startsWith`

startsWith(prefix, ignoreCase) on String Checks that the string starts with prefix. startsWith

`notStartsWith`

notStartsWith(prefix, ignoreCase) on String Checks that the string does not start with prefix. notStartsWith

`endsWith`

endsWith(suffix, ignoreCase) on String Checks that the string ends with suffix. endsWith

`notEndsWith`

notEndsWith(suffix, ignoreCase) on String Checks that the string does not end with suffix. notEndsWith

`matches`

matches(regex) on String Checks that the whole of the string matches regex. matches

`notMatches`

notMatches(regex) on String Checks that the whole of the string does not match regex. A string that only contains a match passes, since the whole string is what is matched. notMatches

Characters

`uppercase`

uppercase() on String Checks that the string has no lowercase letters. Digits, symbols and the empty string pass. uppercase

`lowercase`

lowercase() on String Checks that the string has no uppercase letters. As with uppercase, digits, symbols and the empty string pass. lowercase

`letters`

letters() on String Checks that the string is not empty and has only letters, in any script. letters

`digits`

digits() on String Checks that the string is not empty and has only the digits 0 to 9. digits

`lettersOrDigits`

lettersOrDigits() on String Checks that the string is not empty and has only letters, in any script, and the digits 0 to 9. lettersOrDigits

`ascii`

ascii() on String Checks that the string is not empty and has only ASCII characters. ascii

`containsOnly`

containsOnly(characters) on String Checks that the string is not empty and has only characters from characters. containsOnly

`containsUppercase`

containsUppercase() on String Checks that the string has at least one uppercase letter. containsUppercase

`containsLowercase`

containsLowercase() on String Checks that the string has at least one lowercase letter. containsLowercase

`containsDigit`

containsDigit() on String Checks that the string has at least one of the digits 0 to 9. containsDigit

`containsSymbol`

containsSymbol() on String Checks that the string has at least one character that is not a letter, a digit or whitespace. containsSymbol

`normalized`

normalized(form) on String Checks that the string is already in the Unicode normalization form. normalized

Text that carries a value

`numeric`

numeric() on String Checks that the string is a decimal number, such as 42, -7 or +3.14. There is no exponent and no thousands separator. numeric

`integer`

integer() on String Checks that the string is a whole number, such as 42, -7 or +3. integer

`boolean`

boolean() on String Checks that the string is true or false, in lowercase. boolean

More string formats have pages of their own: internet (email, url, ipv4), identifiers (uuid, isbn), encodings (base64, json), finance (iban, creditCard), dates and countries.

​Length and bytes

​minLength

​maxLength

​length

​lengthBetween

​minBytes

​maxBytes

​Empty and blank

​notEmpty

​empty

​notBlank

​blank

​trimmed

​Comparing with text

​equalTo

​oneOf

​enum

​contains

​notContains

​startsWith

​notStartsWith

​endsWith

​notEndsWith

​matches

​notMatches

​Characters

​uppercase

​lowercase

​letters

​digits

​lettersOrDigits

​ascii

​containsOnly

​containsUppercase

​containsLowercase

​containsDigit

​containsSymbol

​normalized

​Text that carries a value

​numeric

​integer

​boolean

Length and bytes

`minLength`

`maxLength`

`length`

`lengthBetween`

`minBytes`

`maxBytes`

Empty and blank

`notEmpty`

`empty`

`notBlank`

`blank`

`trimmed`

Comparing with text

`equalTo`

`oneOf`

`enum`

`contains`

`notContains`

`startsWith`

`notStartsWith`

`endsWith`

`notEndsWith`

`matches`

`notMatches`

Characters

`uppercase`

`lowercase`

`letters`

`digits`

`lettersOrDigits`

`ascii`

`containsOnly`

`containsUppercase`

`containsLowercase`

`containsDigit`

`containsSymbol`

`normalized`

Text that carries a value

`numeric`

`integer`

`boolean`