refs/tags/1.1.0-nullsafety.1 - string_scanner

commit	a0113de39f11e46600015761972eab4f548e1c0d	[log] [tgz]
author	Nate Bosch <nbosch1@gmail.com>	Tue Sep 22 09:19:17 2020 -0700
committer	GitHub <noreply@github.com>	Tue Sep 22 09:19:17 2020 -0700
tree	93fca1cf4c262b9e6b87e2251938e419d0968116
parent	d51cdb79704cff4d74e7064bafa9fc6b03f84b73 [diff]

tree: 93fca1cf4c262b9e6b87e2251938e419d0968116

README.md

This package exposes a StringScanner type that makes it easy to parse a string using a series of Patterns. For example:

import 'dart:math' as math;

import 'package:string_scanner/string_scanner.dart';

num parseNumber(String source) {
  // Scan a number ("1", "1.5", "-3").
  final scanner = StringScanner(source);

  // [Scanner.scan] tries to consume a [Pattern] and returns whether or not it
  // succeeded. It will move the scan pointer past the end of the pattern.
  final negative = scanner.scan('-');

  // [Scanner.expect] consumes a [Pattern] and throws a [FormatError] if it
  // fails. Like [Scanner.scan], it will move the scan pointer forward.
  scanner.expect(RegExp(r'\d+'));

  // [Scanner.lastMatch] holds the [MatchData] for the most recent call to
  // [Scanner.scan], [Scanner.expect], or [Scanner.matches].
  var number = num.parse(scanner.lastMatch[0]);

  if (scanner.scan('.')) {
    scanner.expect(RegExp(r'\d+'));
    final decimal = scanner.lastMatch[0];
    number += int.parse(decimal) / math.pow(10, decimal.length);
  }

  // [Scanner.expectDone] will throw a [FormatError] if there's any input that
  // hasn't yet been consumed.
  scanner.expectDone();

  return (negative ? -1 : 1) * number;
}