protocols

defprotocol and defimpl macros inspired by Elixir. Under the hood this uses modules and abstract methods to make sure classes claiming to adhere to a certain protocol actually implement it fully.

Installation

Add this to your application's shard.yml:

dependencies:
  protocols:
    github: citizen428/protocols

Usage

require "protocols"

Definining protocols

defprotocol is used for defining new protocols (which will be created as toplevel modules).

defprotocol Greetable do
  def greet
    "Hello from #{name}"
  end

  abstract def name
end

The above form allows us to specify both concrete and abstract methods for the protocol. There is also a shortcut for protocols which only contain abstract methods:

defprotocol Greetable, :greet, :name

Implementing protocols

Given the following Blank protocol

# Returns true if if data is considered blank/empty
defprotocol Blank, :blank?

we can define define an implementation inside a class or struct body:

class Array
  defimpl Blank do
    def blank?
      true
    end
  end
end

nil.blank? #=> true

defimpl will include the protocol module, define a nested module called "#{protocol_name}Implementation" and include this module too. While this may seem complicated, it makes it possible to derive implementations from other classes.

Deriving protocols

To avoid code duplication, it's possible to derive protocol implementations from other classes/structs:

struct Tuple
  derive Blank, from: Array
end

Tuple.new.blank? #=> true

Todo

• Write specs

Contributing

1. Fork it ( https://github.com/citizen428/protocols/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• citizen428 Michael Kohl - creator, maintainer