split method Null safety

List<String> split (
  1. Pattern pattern

Splits the string at matches of pattern and returns a list of substrings.

Finds all the matches of pattern in this string, and returns the list of the substrings between the matches.

var string = "Hello world!";
string.split(" ");                      // ['Hello', 'world!'];

Empty matches at the beginning and end of the strings are ignored, and so are empty matches right after another match.

var string = "abba";
string.split(new RegExp(r"b*"));        // ['a', 'a']
                                        // not ['', 'a', 'a', '']

If this string is empty, the result is an empty list if pattern matches the empty string, and it is [""] if the pattern doesn't match.

var string = '';
string.split('');                       // []
string.split("a");                      // ['']

Splitting with an empty pattern splits the string into single-code unit strings.

var string = 'Pub';
string.split('');                       // ['P', 'u', 'b']

string.codeUnits.map((unit) {
  return new String.fromCharCode(unit);
}).toList();                            // ['P', 'u', 'b']

Splitting happens at UTF-16 code unit boundaries, and not at rune boundaries:

// String made up of two code units, but one rune.
string = '\u{1D11E}';
string.split('').length;                 // 2 surrogate values

To get a list of strings containing the individual runes of a string, you should not use split. You can instead map each rune to a string as follows:

string.runes.map((rune) => new String.fromCharCode(rune)).toList();


List<String> split(Pattern pattern);