Dry::Behaviour

Tiny library inspired by Elixir protocol pattern.

Declaration

require 'dry/behaviour'

module Protocols
  module Adder
    include Dry::Protocol

    defprotocol do
      defmethod :add, :this, :other
      defmethod :subtract, :this, :other

      def add_default(value)
        add(3, 2) + value
      end
    end

    defimpl Protocols::Adder, target: String do
      def add(this, other)
        this * other
      end
      def subtract(this, other)
        this
      end
    end
    defimpl Protocols::Adder, target: NilClass do
      def add(this, other)
        other
      end
      def subtract(this, other)
        this
      end
    end

    # delegate `to_s` as is, map `add` and `subtract` to `:+` and `:-` respectively
    defimpl target: Integer, delegate: :to_s, map: { add: :+, subtract: :- }
  end
end

Usage

expect(Protocols::Adder.add(5, 3)).to eq(8)
expect(Protocols::Adder.add(5, 10)).to eq(15)
expect(Protocols::Adder.subtract(5, 10)).to eq(-5)
expect(Protocols::Adder.add(15, 10)).to eq(25)
expect(Protocols::Adder.add("!", 10)).to eq("!!!!!!!!!!")
expect(Protocols::Adder.add(nil, 10)).to eq(10)

expect(Protocols::Adder.add_default(1)).to eq(6)

Authors

@am-kantox, @saverio-kantox & @kantox

Changelog

0.2.2 :: meaningful errors

Throws an exception on wrong usage:

Protocols::Adder.add({}, 42)
#⇒ Protocols::NotImplemented: Protocol “Protocols::Adder” is not implemented for “Hash”
Protocols::Adder.hello({}, 42)
#⇒ Protocols::NotImplemented: Protocol “Protocols::Adder” does not declare method “hello”

0.2.1 :: multiple targets

Multiple targets:

defimpl MyProto, target: [MyClass1, MyClass2], delegate: [:add, :subtract]

0.2.0 :: implicit delegate on incomplete implementation

when defimpl does not fully cover the protocol declaration, missing methods are implicitly delegated to the target, the warning is being issued:

defimpl MyProto, target: MyClass, map: { add: :+, subtract: :- }
#⇒ W, [2016-10-24T14:52:49.230808 #26382]  WARN -- : Implicit delegate MyProto#to_s to MyClass

0.1.1 :: delegate and map methods to receiver

defimpl now accepts delegate and map:

defimpl MyProto, target: MyClass, delegate: :to_s, map: { add: :+, subtract: :- }

Installation

Add this line to your application's Gemfile:

gem 'dry-behaviour'

And then execute:

$ bundle

Or install it yourself as:

$ gem install dry-behaviour

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]/dry-behaviour. 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.