CharacterRange.at constructor Null safety
Creates a new character iterator on string.
The iterator starts with a current range containing the
substring from startIndex to endIndex of string.
If startIndex is not a character boundary,
the range starts at the beginning of the character
that startIndex is pointing into.
If endIndex is not a character boundary,
the range end at then end of the character
that endIndex is pointing into.
If endIndex is not provided,
it defaults to the same index as startIndex.
So, if no endIndex is provided,
and startIndex is at a character boundary,
the resulting iterator's current range is empty.
Otherwise, the range will contain the characters
of the substring from startIndex to endIndex,
extended so that it contains entire characters of the original string.
Implementation
factory CharacterRange.at(String string, int startIndex, [int? endIndex]) =
StringCharacterRange.at;