RegExp class Null safety

A regular expression pattern.

Regular expressions are Patterns, and can as such be used to match strings or parts of strings.

Dart regular expressions have the same syntax and semantics as JavaScript regular expressions. See ecma-international.org/ecma-262/9.0/#sec-regexp-regular-expression-objects for the specification of JavaScript regular expressions.

The firstMatch method is the main implementation method that applies a regular expression to a string and returns the first RegExpMatch. All other methods in RegExp can be build from that.

The following example finds the first match of a regular expression in a string.

RegExp exp = RegExp(r'(\w+)');
String str = 'Parse my string';
RegExpMatch? match = exp.firstMatch(str);
print(match![0]); // "Parse"

Use allMatches to look for all matches of a regular expression in a string.

The following example finds all matches of a regular expression in a string.

RegExp exp = RegExp(r'(\w+)');
String str = 'Parse my string';
Iterable<RegExpMatch> matches = exp.allMatches(str);
for (final m in matches) {
  print(m[0]);
}

The output of the example is:

Parse
my
string

Note the use of a raw string (a string prefixed with r) in the example above. Use a raw string to treat each character in a string as a literal character.