SOKERR

Simple OK Err

Simple Result sum type for Dart

Why?

There are already many other packages that offer a similar implementation of a Result type, the problem is that all of them try to do too many things at the same time, like implementing methods that could be simply avoided by using Dart's switch expressions. So I decided to implement my own SIMPLE Result.

I found myself copy-pasting this code on all my new projects and got tired of it. So here we are.

Examples

Return a Result from a function

Future<Result<(), String>> updateTable() async {
  ...
  if (somethingWentWrong) {
    return Err("My error");
  }
  ...

  /// Want to know if successful but don't want to return anything?
  /// return an empty pattern `()`
  return Ok(());
}

Wrap a Future (extension)

Future<Result<String, Object?>> mySafeFunction() async {
  final res = await unsafeFutureFromAPackageIDidNotWrite().result();

  ...

  return switch (res) {
    Ok(:final ok) => () {
        ...
        return Ok("");
      }(),
    Err() => res,
  };
}

Wrap a Function (extension)

void main() {
  /// JWT's constructor throws an exception when the token has expired
  final res = (() => JWT.verify(token, SecretKey(secret))).result();
  ...
}

How can I map a result?

void main() {
  final Result<Data, ()> res = getResult();

  final orElse = "orElse";

  final String mappedValue = switch (res) { Ok(:final ok) => ok.myVal, Err() => orElse };
}