gmana_predicates 0.0.3 
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gmana.coPure Dart boolean predicate functions for string classification — email, alpha, date, UUID, credit card, and more.
gmana_predicates #
Pure Dart boolean predicate functions and fluent extensions for string classification and validation.
import 'package:gmana_predicates/gmana_predicates.dart';
// Standalone functions
if (isEmail(userInput)) { ... }
// Fluent extension syntax
if (userInput.isEmail) { ... }
All functions are top-level and pure — no classes, no state, no side effects. Functions marked @experimental are subject to change or removal.
Table of contents #
Composing predicates #
Every predicate here is a bool Function(String), which is exactly
Predicate<String>. That makes them composable without any wrapping.
final username = Predicates.all<String>([
isNotBlank,
(value) => value.isLength(3, 16),
isAlphaNumeric.or(isSnakeCase),
]);
username('sun_sreng'); // true
username('ab'); // false — too short
username('has spaces'); // false
The combinators #
Predicates.all([a, b]) // every one passes; short-circuits, empty = true
Predicates.any([a, b]) // at least one passes; short-circuits, empty = false
Predicates.none([a, b]) // no one passes
Predicates.not(a) // negation
Predicates.alwaysTrue() // identity element for `all`
Predicates.alwaysFalse()
Predicates.equalTo('draft')
Predicates.oneOf(['draft', 'review']) // set membership
Predicates.nullable(isEmail, whenNull: true) // lift to Predicate<String?>
They are static members rather than top-level functions so that names as
common as all, any and not stay out of your global namespace — and so
they do not clash with the matchers of the same name in package:test.
The fluent form #
isEmail.and(isNotBlank) // right side skipped when the left fails
isEmail.or(isUrl) // right side skipped when the left passes
isNumeric.xor(isAlpha) // both sides always run
isEmail.negated
isNumeric.everyIn(['1', '2']) // true
isNumeric.anyIn(['1', 'x']) // true
on retargets a Predicate<String> at a field of a larger object, so the
same rules work on records and models:
final hasValidEmail = isEmail.on((User user) => user.email);
final invalid = users.where(hasValidEmail.negated);
Fluent Extensions #
All predicates are also available as fluent getters and methods on String?, String, and DateTime:
'user@example.com'.isEmail // true
'192.168.1.1'.isIpv4 // true
'42'.isEven // true
'7'.isPrimeString // true
'01ARZ3NDEKTSV4RRFFQ69G5FAV'.isULID // true
String? name;
name.isBlank // true
name.isNotBlank // false
DateTime.now().isWeekend // true/false
Using this through
package:gmana?gmana_extensionsdeclares some of the same names onString—isAlpha,isEmail,isNumeric,isUrl,containsIgnoreCase, and the date predicatesisDate,isAfter,isBefore,isBetween,isToday,isPast,isFuture,isWeekday,isWeekend,isLeapYear. When both libraries are in scope Dart reports those calls as ambiguous. Use the top-level function form (isEmail(value)), which is never ambiguous, or an explicit extension override:GmanaStringPredicatesX(value).isEmail.
String #
Character set & case #
isAlpha('Hello') // true — ASCII letters only (a–z, A–Z)
isAlphaNumeric('A1b2') // true — ASCII letters and digits only
isAscii('hello') // true — printable ASCII (U+0000–U+007F)
isNumeric('42') // true — digits only (optionally negative)
isInt('42') // true
isFloat('3.14') // true
isBase64('SGVsbG8=') // true
isHexadecimal('FF5500') // true
isHexColor('#FF5500') // true
isLowerCase('hello') // true
isUpperCase('HELLO') // true
isCapitalized('Hello') // true — starts with uppercase letter
Case & naming conventions #
isCamelCase('camelCaseStr') // true
isPascalCase('PascalCaseStr') // true
isSnakeCase('snake_case_str') // true
isKebabCase('kebab-case-str') // true
isScreamingSnakeCase('FOO_BAR') // true
isTitleCase('Foo Bar Baz') // true — rejects `Foo BAR`
Number bases & encodings #
isBinary('01101') // true
isOctal('0755') // true
isBase32('MZXW6YTB') // true — RFC 4648, uppercase alphabet
isDecimal('12.50', places: 2) // true — exactly two decimal places
isDecimal('12.5', places: 2) // false
Colors & coordinates #
isRgbColor('rgb(255, 0, 128)') // true — channels must be 0–255
isHslColor('hsl(210, 50%, 40%)') // true — percentages must be 0–100
isLatitude('11.55') // true — -90..90
isLongitude('104.91') // true — -180..180
isLatLong('11.55,104.91') // true
Passwords #
isStrongPassword(r'Tr0ub4dor&3') // true
// Every rule can be switched off independently
isStrongPassword(
candidate,
minLength: 12,
requireSpecial: false,
allowWhitespace: true, // passphrases
);
Text shape #
isPrintable('Hello!') // true — printable ASCII + \t \n \r
hasWhitespace('a b') // true
startsWithIgnoreCase('HelloWorld', 'hello') // true
endsWithIgnoreCase('HelloWorld', 'WORLD') // true
isAnagram('Dormitory', 'Dirty Room') // true — ignores case/punctuation
Format & validation #
isEmail('user@example.com') // true
isSlug('my-blog-post') // true
isJson('{"a":1}') // true
isJwt('eyJhbGci...') // true — JSON Web Token structure
isMimeType('application/json')// true — RFC 2045 MIME type
isHash('5d41402...', 'md5') // true — md5, sha1, sha256, sha512
isPalindrome('racecar') // true — ignores non-alphanumeric/case by default
Null & whitespace checks #
isNullOrEmpty(null) // true
isBlank(' \t') // true — null, empty, or whitespace-only
isNotBlank('hello') // true — not null and contains non-whitespace
Experimental #
isFullWidth('Ａ') // true — full-width Unicode
isHalfWidth('A') // true — half-width Unicode
isMultiByte('héllo') // true — contains non-ASCII
isSurrogatePair('𝄞') // true — contains surrogate pairs
isVariableWidth('Aａ') // true — mixed half and full-width
Date #
isDate('2024-06-15') // true
isTime('14:30:00') // true — 24-hour time format
isToday('2024-06-15') // true/false depending on today UTC
isPast('2020-01-01') // true
isFuture('2099-12-31') // true
isAfter('2024-12-31', '2024-01-01') // true
isBefore('2020-01-01', '2021-01-01') // true
isBetween('2024-06-15', '2024-01-01', '2024-12-31') // true
isWeekend('2024-01-13') // true
isWeekday('2024-01-15') // true
isLeapYear('2024-02-01') // true
isSameDay('2026-08-07T10:00Z', '2026-08-07T18:00Z') // true
isSameMonth('2026-08-01', '2026-08-31') // true
isSameYear('2026-01-01', '2026-12-31') // true
isSameWeek('2024-06-10', '2024-06-16') // true — Monday-start week
Relative to now #
isYesterday('2026-08-06') // true/false vs today UTC
isTomorrow('2026-08-08')
isWithinLast(signupDate, const Duration(days: 30))
isWithinNext(dueDate, const Duration(days: 7))
isAgeAtLeast('2000-01-01', 18) // true — the birthday itself counts
Boundaries & strictness #
isStartOfMonth('2024-06-01') // true
isEndOfMonth('2024-02-29') // true — leap-year aware
// isBetween is exclusive; isBetweenInclusive admits the bounds
isBetween('2024-01-01', '2024-01-01', '2024-12-31') // false
isBetweenInclusive('2024-01-01', '2024-01-01', '2024-12-31') // true
// isIso8601 is stricter than isDate
isDate('2024-06-15 10:00:00') // true — DateTime.tryParse accepts it
isIso8601('2024-06-15 10:00:00') // false — not the T form
isDate('2024-13-01') // true — silently rolls into 2025
isIso8601('2024-13-01') // false
How dates are parsed #
A string with no time and no zone names a calendar day and is read as UTC midnight, so these predicates give the same answer in every timezone. A value that does carry a time but no zone is treated as local, since a wall-clock reading without a zone is a local one.
tryParseDate('2024-06-15') // 2024-06-15 00:00:00.000Z
tryParseDate('2024-06-15T10:30:00') // local 10:30, converted to UTC
tryParseDate('2024-06-15T10:30:00Z') // 2024-06-15 10:30:00.000Z
Network #
isIpv4('192.168.0.1') // true
isIpv6('::1') // true
isIP('192.168.0.1', 4) // true — version check
isCidr('192.168.1.0/24') // true — CIDR block notation
isUrl('https://example.com/api') // true
isMacAddress('00:1A:2B:3C:4D:5E') // true
isPort('8080') // true
isDataURI('data:image/png;base64,...') // true — RFC 2397
isMagnetURI('magnet:?xt=urn:btih:...') // true — BitTorrent Magnet
isPostalCode('90210', 'US') // true
isHostname('localhost') // true — no TLD required
isHostname('sub.example.com') // true
Address classification #
isPrivateIpv4('10.0.0.1') // true — RFC 1918: 10/8, 172.16/12, 192.168/16
isLoopbackIpv4('127.0.0.1') // true — the whole 127/8 block
isPublicIpv4('8.8.8.8') // true
isPublicIpv4('169.254.1.1') // false — link-local
isPublicIpv4('224.0.0.1') // false — multicast and above
Identifiers #
isUuid('550e8400-e29b-41d4-a716-446655440000') // true
isCreditCard('4111111111111111') // true — Luhn check
isLuhnValid('79927398713') // true — standalone Luhn check
isIMEI('490154203237518') // true — 15-digit IMEI
isEAN('4006381333931', '13') // true — EAN-8 / EAN-13
isULID('01ARZ3NDEKTSV4RRFFQ69G5FAV') // true — Crockford Base32
isNanoId('V1StGXR8_Z5jdHi6B-myT') // true — Nano ID check
isSemVer('1.0.0-alpha.1') // true
isPhoneNumber('+1 (415) 555-2671') // true
isIban('GB82 WEST 1234 5698 7654 32') // true — ISO 13616 mod-97
isBic('DEUTDEFF') // true — 8- or 11-character
// isUuid takes a version: '1', '3', '4', '5', '6', or '7'
isUuid('018f7b1a-9c2e-7d3f-8a4b-5c6d7e8f9a0b', '7') // true
// Experimental
isISBN('978-3-16-148410-0') // true
isMongoId('507f1f77bcf86cd799439011') // true
isFQDN('example.com') // true
Numeric #
isDivisibleBy('9', '3') // true
isEven('42') // true
isOdd('7') // true
isPositive('15.5') // true
isNegative('-10') // true
isZero('0.0') // true
isInRange('5', 1, 10) // true
isPrime(29) // true — integer input
isPrimeString('29') // true — string input
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Pure Dart boolean predicate functions for string classification — email, alpha, date, UUID, credit card, and more.
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Topics
#validation #predicates #utility
License
MIT (license)