Dart Runes

In Dart, strings are represented as sequences of Unicode UTF-16 code units. The Unicode format maps a unique numeric character to each letter, digit, and symbol. The code below shows Unicode equivalents of some characters.

import 'dart:convert';

void main() {

    //Unicode equivalent of uppercase M

    var uppercaseM = '\u{004d}';

    print(uppercaseM);



    //Unicode equivalent of the digit 7

    var seven = '\u{0037}';

    print(seven);



    //Unicode equivalent of the the dollar sign

    var dollarSign = '\u{0024}';

    print(dollarSign);



    //Unicode equivalent of the thumbs-up emoji

    var thumbsUp = '\u{1f44d}';

    print(thumbsUp);    

}

A rune is an integer that represents a Unicode code point. The dart:core library allows runes to be accessed from Dart strings. There are three main methods used for this purpose:

  1. String.codeUnitAt(int index)
    This function takes in the index of a code unit in a string and returns the unit in 16-bit UTF-16 (decimal) format.
import 'dart:convert';
void main() {
    String string = 'Educative';
    //UTF-16 code unit for 'd' at second index of string
    print(string.codeUnitAt(1));
    //UTF-16 code unit for 't' at sixth index of string
    print(string.codeUnitAt(5));
}
  1. String.codeUnits
    This property outputs an unmodifiable list of all the corresponding UTF-16 code units of the string.
import 'dart:convert';

void main() {

    String string = 'Educative';



    //UTF-16 code unit list for the string above

    print(string.codeUnits);

}
  1. String.runes
    This enables iteration through code units.
import 'dart:convert';

void main() {

    String string = 'Educative';



    //Iterating over Unicode code-points of the string above

    string.runes.forEach((int rune) { 

      var char=new String.fromCharCode(rune); 

      print(char); 

   });

}
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