How to get substring between two strings in DART?

Question

How can i achieve similar solution to: How to get a substring between two strings in PHP? but in DART

For example I have a String:
String data = "the quick brown fox jumps over the lazy dog"
I have two other Strings: quick and over
I want the data inside these two Strings and expecting result:
brown fox jumps

score 75 · Accepted Answer · edited Nov 19 '19 at 19:39

75

You can use String.indexOf combined with String.substring:

void main() {
  const str = "the quick brown fox jumps over the lazy dog";
  const start = "quick";
  const end = "over";

  final startIndex = str.indexOf(start);
  final endIndex = str.indexOf(end, startIndex + start.length);

  print(str.substring(startIndex + start.length, endIndex)); // brown fox jumps
}

Note also that the startIndex is inclusive, while the endIndex is exclusive.

edited Nov 19 '19 at 19:39

Dominik Palo

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answered Jul 24 '19 at 15:30

Rémi Rousselet

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I was almost about to post an answer with `RegExp`. But this one's better – Ajil O. Jul 24 '19 at 15:33
My String is actually unformatted `HTML` and is very long. `substring` method failed with RangeError. So, @Sergey Solodukhin's answer worked for me. This one is awesome for smaller Strings. Thank you. – Sukhchain Singh Jul 24 '19 at 16:10
@SukhchainSingh it was a bug. I've just fixed it – Rémi Rousselet Jul 24 '19 at 16:14
@RémiRousselet Thank you, it worked. It's lot faster than regexp as expected :) – Sukhchain Singh Jul 24 '19 at 18:28
What's about real data? Word order may change "the over quick brown fox jumps the lazy dog" or one keyword may be absent. – Spatz Jul 24 '19 at 18:34
@SergeySolodukhin No it's not absent in my case and order will be not changed too. – Sukhchain Singh Jul 25 '19 at 04:08

Spatz · Answer 2 · 2019-07-24T18:49:51.740

9

I love regexp with lookbehind (?<...) and lookahead (?=...):

void main() {
  var re = RegExp(r'(?<=quick)(.*)(?=over)');
  String data = "the quick brown fox jumps over the lazy dog";
  var match = re.firstMatch(data);
  if (match != null) print(match.group(0));
}

edited Jul 24 '19 at 18:49

answered Jul 24 '19 at 15:48

Spatz

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Thank you, my string was very large so [Rémi Rousselet's](https://stackoverflow.com/a/57186482/7814638) answer didn't helped. This one worked like a charm. – Sukhchain Singh Jul 24 '19 at 16:08

score 4 · Answer 3 · answered May 30 '20 at 16:03

4

final str = 'the quick brown fox jumps over the lazy dog';
final start = 'quick';
final end = 'over';

final startIndex = str.indexOf(start);
final endIndex = str.indexOf(end);
final result = str.substring(startIndex + start.length, endIndex).trim();

answered May 30 '20 at 16:03

CopsOnRoad

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score 2 · Answer 4 · answered Jul 21 '22 at 17:02

For future researchers: To start form the beginning of a string to a specific symbol or character;

Using substring and indexOf which is faster than regExp do this:

void main() {
  const str = "Cars/Horses";

  final endIndex = str.indexOf("/", 0);

  print(str.substring(0, endIndex)); // Cars
}

This might just help someone

score 1 · Answer 5 · answered Jul 24 '19 at 15:39

You can do that with the help of regex. Create a function that will return the regex matches as

Iterable<String> _allStringMatches(String text, RegExp regExp) => 
regExp.allMatches(text).map((m) => m.group(0));

And then define your regex as RegExp(r"[quick ]{1}.*[ over]{1}"))

score 0 · Answer 6 · answered Apr 19 '22 at 13:08

The substring functionality isn't that great, and will throw errors for strings above the "end" value.

To make it simpler user this custom function that doesn't thrown an error, instead using the max length.

String substring(String original, {required int start, int? end}) {
  if (end == null) {
    return original.substring(start);
  }
  if (original.length < end) {
    return original.substring(start, original.length);
  }
  return original.substring(start, end);
}

How to get substring between two strings in DART?

6 Answers6