`unicodeToList`

Splits a string into user-perceived characters, correctly handling surrogate pairs.

List<String> unicodeToList(String s)

Lecture

Dart Strings are sequences of UTF-16 code units, not characters. Calling s.split('') splits by code unit — fine for plain ASCII/Latin text, but wrong for anything outside the Basic Multilingual Plane, like most emoji: those are represented as a surrogate pair (two code units), so a naive split tears a single emoji into two broken halves.

unicodeToList fixes that by iterating the string's .runes — Unicode code points — and turning each one back into its own single-character String. The result is the list of characters a person actually sees when reading the string, matching FxTS's unicodeToList, which splits by code point rather than UTF-16 unit.

Demo 1 · Naive split vs. unicodeToList

Demo 2 · Reversing and counting correctly

Building on unicodeToList, a naive-split reverse would mangle the emoji; this one doesn't:

Try it yourself

Exercise: count how many user-perceived characters are in this string (it contains an emoji).

Related: split — split on a plain char iterable · reverse — reverse an Iterable, same surrogate-pair care applies to strings · countBy — used above to tally characters · identity — used above as the counting key