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Result types (like in Rust) in Ruby
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README.md

Opted

Inspired by Rust's Result type, this gem provides basic value types to represent success (Ok) and failure (Err) results.

Note: this is mostly experimental. Since I've only used this for trivial things so far, I suggest using caution before using this anywhere important.

Installation

Add this line to your application's Gemfile:

gem 'opted'

And then execute:

$ bundle

Usage

# This gem doesn't polute the top-level namespace
# so it can be handy to alias the classes
Ok = Opted::Result::Ok
Err = Opted::Result::Err

# This code sample is run as a part of this gem's test suite
def assert(value)
  fail "Invalid assertion in README code sample" unless value
end

assert Ok.new(1).unwrap! == 1

begin
  Err.new(:whoops).unwrap!
rescue Opted::Result::UnwrapError => e
  assert e.message =~ /Called #unwrap! on #<Opted::Result::Err:.* @error=:whoops>/
else
  fail
end

result = Ok.new(1)

unwrapped_result = result.match do
  ok { |value| value + 1 }
  err { |error| fail "unreachable" }
end

assert unwrapped_result == 2

# disallows wrapping nil
begin
  Ok.new(nil)
rescue ArgumentError => e
  assert e.message =~ /can't wrap nil/
else
  fail
end

begin
  Err.new(nil)
rescue ArgumentError => e
  assert e.message =~ /can't wrap nil/
else
  fail
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/opted. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Opted project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

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