RSL - Result Simple Library

A minimal, zero-dependency Result type implementation for Dart with standalone Right/Left constructors similar to dartz.

Features

• 🚀 Simple API with Right() and Left() constructors
• 🛡️ Type-safe error handling
• 🔄 Functional operations (map, flatMap, fold)
• 📦 Zero dependencies
• 🧪 Full test coverage
• 💯 Null safety

Installation

Add to your pubspec.yaml:

dependencies:
  rsl: ^1.0.0

Usage

Basic Example

import 'package:rsl/rsl.dart';

Result<String, int> parseNumber(String input) {
  try {
    return Right(int.parse(input));
  } catch (e) {
    return Left('Invalid number: $input');
  }
}

void main() {
  final result = parseNumber('42');
  
  // Pattern matching
  result.fold(
    (error) => print('Error: $error'),
    (number) => print('Success: $number'),
  );
  
  // Get value with fallback
  final value = result.getOrElse(() => 0);
  print(value); // 42
}

API Reference

Constructors

• Right(value) - Success result
• Left(error) - Failure result

Methods

• isRight/isLeft - Check result type
• right/left - Get value (throws if wrong type)
• fold(ifLeft, ifRight) - Pattern matching
• map(f) - Transform success value
• mapLeft(f) - Transform failure value
• flatMap(f) - Chain operations

Extensions

• getOrElse(orElse) - Get value or fallback
• getOrNull() - Get value or null
• getOrThrow() - Get value or throw error
• swap() - Swap success/failure values

Comparison with dartz

RSL provides a simpler alternative to dartz's Either type when you just need basic Result-type functionality:

// With dartz
Either<String, int> result = Right(42);

// With rsl
Result<String, int> result = Right(42);

License

MIT - See LICENSE for details.