Dart & Flutter: Convert String/Number to Byte Array (Byte List)

This concise article shows you how to convert a string or a number (integer or double) to a byte array (a list of bytes) in Dart (and Flutter as well).

Converting a String into a Byte Array

There is more than one way to turn a given string into a byte array in Dart.

Using the utf8.encode() method

The utf8.encode() method (which can be imported from dart:convert) takes a string and return a list of UTF-8 bytes.

Example:

// main.dart
import 'dart:convert';

void main() {
  String text = 'KindaCode.com';
  List<int> bytes = utf8.encode(text);
  print(bytes);
}

Output:

[75, 105, 110, 100, 97, 67, 111, 100, 101, 46, 99, 111, 109]

Using the codeUnits property of the String class

The codeUnits property of the String class returns a list of UTF-16 code units.

Example:

// main.dart
void main() {
  String text = 'KindaCode.com';
  List<int> bytes = text.codeUnits;
  print(bytes);
}

Output:

75, 105, 110, 100, 97, 67, 111, 100, 101, 46, 99, 111, 109]

Using the runes property of the String class

The runes property gives you an iterable of Unicode code points of a string.

Example:

// main.dart
void main() {
  String text = 'Welcome to KindaCode.com';
  Iterable<int> bytes = text.runes;

  // convert the iterable to a list
  List<int> list = bytes.toList();
  print(list);
}

Output:

[87, 101, 108, 99, 111, 109, 101, 32, 116, 111, 32, 75, 105, 110, 100, 97, 67, 111, 100, 101, 46, 99, 111, 109]

Converting a Number into a Byte Array

To convert a number to a byte array, you can first convert it to a string and then use one of the approaches mentioned in the previous section to get the job done.

Example:

// main.dart
import "dart:convert";

void main() {
  // integer to byte array
  int myInt = 2023;
  print(utf8.encode(myInt.toString()));

  // double to byte array
  double myDouble = 3.1416;
  print(utf8.encode(myDouble.toString()));
}

Output:

[50, 48, 50, 51]
[51, 46, 49, 52, 49, 54]

That’s it. Further reading:

• Flutter & Dart: Convert a String/Integer to Hex
• Flutter & Dart: Convert Strings to Binary
• How to Create a Stopwatch in Flutter
• Flutter & SQLite: CRUD Example
• Using Provider for State Management in Flutter
• Flutter: Turn an Image into a Base64 String and Vice Versa

You can also tour around our Flutter topic page or Dart topic page for the most recent tutorials and examples.