Chainable Methods

The Elixir language is doing great and within its many incredible features is the famour "Pipe Operator".

It allows you to do constructs such as this:

1..100_000
  |> Stream.map(&(&1 * 3))
  |> Stream.filter(odd?)
  |> Enum.sum

In a nutshell, this is taking the previous returning value and automatically passing as the first argument of the following function call, so it's equivalent to do this:

Enum.sum(Enum.filter(Enum.map(1..100_000, &(&1 * 3)), odd?))

This is how we would usually do it, but with the Pipe Operator it becomes incredibly more enjoyable and readable to work with and shifts our way of thinking into making small functions in linked chains. (By the way, this example comes straight from Elixir's Documentation)

Now, in the Ruby world, we would prefer to do it in a more Object Oriented fashion, with chained methods like this:

object.method_1.method_2(argument).method_3 { |x| do_something(x) }.method_4

This is how we do things in Rails, for example, Arel coming into mind:

User.first.comments.where(created_at: 2.days.ago..Time.current).limit(5)

This pattern involves the methods returning "self" and further methods changing the internal state of the object.

On the other hand, sometimes we would want to just be able to take adhoc returning objects and passing them ahead and isolating on the methods level instead of the objects level. There is a lot of existing discussions so the idea is not to vouch for one option or the other.

In case you want to do the "semi-functional" way, we can do it like this:

Installation

Add this line to your application's Gemfile:

gem 'chainable_methods'

And then execute:

$ bundle

Or install it yourself as:

$ gem install chainable_methods

Usage

# create your Module with composable 'functions'
module MyModule
  extend ChainableMethods

  def self.method_a(current_state)
    # transform the state
    do_something(current_state)
  end

  def self.method_b(current_state, other_argument)
    do_something2(current_state, other_argument)
  end

  def self.method_c(current_state)
    yield(current_state)
  end
end

And now we can build something like this:

MyModule.
  chain_from(some_text).
  upcase. # this calls a method from the string in 'some_text'
  method_a.
  method_b("something").
  method_c { |current_state| do_something3(current_state) }.
  unwrap

And that's it. This would be the equivalent of doing something more verbose like this:

a = some_text.upcase
b = MyModule.method_a(a)
c = MyModule.method_b(b, "something")
d = MyModule.method_c(c) { |c| do_something3(c) }

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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/akitaonrails/chainable_methods. 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.

CHANGELOG

v0.1.0

initial version

v0.1.1

introduces the ability to wrap any plain ruby object, without the need for a special module to extend the ChainableMethods module first.
fixes the priority of methods to call if both state and context has the same method, context always has precedence

v0.1.2

introduces a shortcut global method 'CM' to be used like this:

CM(2, ['a', 'b', 'c'])
  .[]
  .upcase
  .unwrap
# => "C"

v0.1.3

introduces the #chain method do link blocks of code together, the results are wrapped in the Link object and chained again

CM("foo http:///www.google.com bar")
.chain { |text| URI.extract(text) }
.first
.chain { |url| URI.parse(url) }
.chain { |uri| open(uri) }
.read
.chain { |body| Nokogiri::HTML(body) }
.css("h1")
.first.text.strip
.unwrap

License

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