How can I decode a hexadecimal to a byte array in Dart?

Question

So there's the 'dart:convert' library, which contains a HexDecoder class that doesn't seem to have a constructor (according to this). But importing it and trying to construct it doesn't work; I thought maybe there was a default constructor not mentioned.

I could copy the code in the source for the convert method, but I'd rather make this a learning opportunity. Any help would be appreciated.

Answer 1

HexDecoder isn't actually in dart:convert. It's in a package (also) called convert.

You need to add it to your pubspec.yaml and then use an import like:

import 'package:convert/convert.dart';

Then use it like this:

  hex.decode('abcdef');

hex is a const singleton instance of the codec. (The constructor is private; you don't need to instantiate your own - use the existing const instance.)

Answer 2

For anyone who wants to convert hexadecimal numbers to 2's component, Dart has a builtin method .toSigned(int):

var testConversion = 0xC1.toSigned(8);
print("This is the result: " + testConversion.toString()); // prints -63