regex_builder 0.1.0+5

A declarative builder for Regex.

A declarative way to write regular expressions in Dart. This package was inspired by Swift RegexBuilder.

Important: This package is still in development and could change until the first stable release.

Features

RegexBuilder conforms with RegExp, thus all methods and properties are available to use.

The following example finds all matches of word in a string.

final regex = RegexBuilder([
  Group([OneOrMore(CharacterSet.word)])
]);

final str = 'Parse my string';
Iterable<RegExpMatch> matches = regex.allMatches(str);
for (final m in matches) {
  print(m[0]);
}

The output of the example is:

Parse
my
string

Components

A RegexBuilder is composed of a list of components. The following components are available:

• Literal
• Wildcards
• Alternation
• Quantifiers
  • ZeroOrMore
  • OneOrMore
  • Optionally
  • Repeat
• CharacterSet
• Group
  • Capture
• Anchor

Literal

A literal is a string of characters that must be matched exactly.

const RegexComponent abc = Literal('abc'); // This represents the pattern 'abc'

Wildcards

A wildcard is a character that matches any character.

const RegexComponent anyCharacter = AnyCharacter(); // This represents the pattern '.'

Alternation

An alternation is a list of components that could match any of them.

const RegexComponent carOrDog = ChoiceOf([
  Literal('cat'),
  Literal('dog'),
]); // This represents the pattern 'cat|dog'

Quantifiers

Quantifiers are used to specify how many times a component should be matched.

ZeroOrMore

Matches zero or one time.

const RegexComponent zeroOrMore = ZeroOrMore(Literal('a')); // This represents the pattern 'a*'

OneOrMore

Matches one or more times.

const RegexComponent oneOrMore = OneOrMore(Literal('a')); // This represents the pattern 'a+'

Optionally

Matches zero or one time.

const RegexComponent optionally = Optionally(Literal('a')); // This represents the pattern 'a?'

Repeat

Matches a specific number of times.

const RegexComponent repeatAtLeast = Repeat(
  Literal('a'),
  range: RepeatRange.atLeast(3),
); // This represents the pattern 'a{3,}'

const RegexComponent repeatAtMost = Repeat(
  Literal('a'),
  range: RepeatRange.atMost(3),
); // This represents the pattern 'a{0,3}'

const RegexComponent repeatExactly = Repeat(
  Literal('a'),
  range: RepeatRange.exactly(3),
); // This represents the pattern 'a{3}'

const RegexComponent repeatBetween = Repeat(
  Literal('a'),
  range: RepeatRange.between(3, 5),
); // This represents the pattern 'a{3,5}'

CharacterSet

Group

A group is a list of components that must be matched together. By default, a group is non-capturing.

const RegexComponent group = Group([
  Literal('a'),
  Literal('b'),
]); // This represents the pattern '(?:ab)'

Capture

A capture group is a list of components that must be matched together and will be captured.

const RegexComponent unnamedCapture = Group([
  Literal('a'),
  Literal('b'),
], behavior: GroupBehavior.capture()); // This represents the pattern '(ab)'

const RegexComponent namedCapture = Group([
  Literal('a'),
  Literal('b'),
], behavior: GroupBehavior.capture('group_name')); // This represents the pattern '(?<group_name>ab)'

Anchor

An anchor is a component that matches the beginning or end of a string.

const RegexComponent startOfSLine = Anchor.startOfLine; // This represents the pattern '^'
const RegexComponent endOfLine = Anchor.endOfLine; // This represents the pattern '$'