DCI with delegation instead of extension

dci_alt.rb

class User < ActiveRecord::Base
  # ... lots of persistence stuff
end

class GitHubUserProvisioner < SimpleDelegator
  def provision_with!(user_info, extra_user_hash)
    self.github_login = extra_user_hash['login']
    self.name = user_info['name']
    self.email = user_info['email']
    self.github_url = user_info['urls']['GitHub']
    self.blog_url = user_info['urls']['Blog']
    self.gravatar_id = extra_user_hash['gravatar_id']
    self.location = extra_user_hash['location']
    save!
  end 
end

# And, say, in your SessionController in your controller action

class SessionController < ApplicationController
  def create
    user = User.new
    provisioner = GitHubUserProvisioner.new(user)
    provisioner.provision_with!(*yank_oauth_stuff_off_request)
  end

  private

  def yank_oauth_stuff_off_request
    # ...
  end
end

From the blog: http://evan.tiggerpalace.com/articles/2011/11/24/dci-that-respects-the-method-cache/

I’ve been toying with DCI lately. But the techniques spelled out to date here and here use Object.extend. Extending an object blows away the method cache, slightly reducing performance.

So, as I lazed in bed, reading this tweet while dreaming of turkey to come, it hits me: instead of implementing the Delegator pattern through extend, let’s just use an actual Delegator object.

Simple example below based on the usage of NewUserProvisioner within RubyPair.

Our good friend SimpleDelegator is defined in “delegate.rb” in stdlib, courtesy of James Edward Gray II.

Another reference: https://tonyarcieri.com/dci-in-ruby-is-completely-broken

A book on DCI & Ruby: http://clean-ruby.com/