Dart: How to Convert a List/Map into Bytes

Bytes are units of digital information that represent binary data. A byte consists of eight bits, which are either 0 or 1. This concise, example-based article will show you how to convert a list or a map into bytes in Dart (and Flutter as well). Let’s begin!

Convert a List to Bytes

To turn a list into bytes, you can use the Utf8Codec class, which encodes and decodes strings using the UTF-8 format. UTF-8 is a standard way of representing text using bytes. You can create an instance of Utf8Codec and call its encode method with the list as the argument. The encode method will return a list of bytes that represents the original list as a string.

Example:

import 'dart:convert';
import 'package:flutter/foundation.dart' show kDebugMode;

void main() {
  // a list of numbers
  final list1 = [1, 2, 3];
  // a list of strings
  final list2 = ['a', 'b', 'kindacode.com'];

  // Convert the list into bytes using Utf8Codec
  const codec = Utf8Codec();

  final bytesList1 = codec.encode(list1.toString());
  final bytesList2 = codec.encode(list2.toString());

  if (kDebugMode) {
    print(bytesList1);
    print(bytesList2);
  }
}

Output:

[91, 49, 44, 32, 50, 44, 32, 51, 93]
[91, 97, 44, 32, 98, 44, 32, 107, 105, 110, 100, 97, 99, 111, 100, 101, 46, 99, 111, 109, 93]

Convert a Map to Bytes

In order to turn a map into bytes, you can use the JsonCodec class, which encodes and decodes objects using the JSON format. JSON is a standard way of representing data using strings. You can create an instance of JsonCodec and call its encode method with the map as the argument. The encode method will return a string that represents the original map as a JSON object. Then, you can use the Utf8Codec class to convert the string into bytes, as explained above.

Example:

import 'dart:convert';
import 'package:flutter/foundation.dart' show kDebugMode;

void main() {
  final map = {'key1': 'foo bar', 'key2': 123, 'key3': 'kindacode.com'};

  const jsonCodec = JsonCodec();

  final jsonMap = jsonCodec.encode(map);
  final bytesMap = const Utf8Codec().encode(jsonMap);
  if (kDebugMode) {
    print(bytesMap);
  }
}

Output:

[123, 34, 107, 101, 121, 49, 34, 58, 34, 102, 111, 111, 32, 98, 97, 114, 34, 44, 34, 107, 101, 121, 50, 34, 58, 49, 50, 51, 44, 34, 107, 101, 121, 51, 34, 58, 34, 107, 105, 110, 100, 97, 99, 111, 100, 101, 46, 99, 111, 109, 34, 125]

That’s it. Further reading:

• Using Try-Catch-Finally in Dart (3 examples)
• Using List.generate() in Flutter and Dart (4 examples)
• Flutter: Global, Unique, Value, Object, and PageStorage Keys
• Flutter AnimatedList – Tutorial and Examples
• Using Dio to fetch data in Flutter (with example)
• How to Create a Stopwatch in Flutter
• Flutter StreamBuilder: Tutorial & Examples (Updated)

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