class StereoPlayer
  def method_missing(method, *args, &block)
    if method.to_s =~ /play_(\w+)/
      puts "Here's #{$1}"
    else
      super
    end
  end
end

p = StereoPlayer.new
# ok:
p.play_some_Beethoven # => "Here's some_Beethoven"
# not very polite:
p.respond_to? :play_some_Beethoven # => false

class StereoPlayer
  # def method_missing ...
  #   ...
  # end

  def respond_to?(method, *)
    method.to_s =~ /play_(\w+)/ || super
  end
end
p.respond_to? :play_some_Beethoven # => true

p.method :play_some_Beethoven
# => NameError: undefined method `play_some_Beethoven'
#               for class `StereoPlayer'

class StereoPlayer
  # def method_missing ...
  #   ...
  # end

  def respond_to_missing?(method, *)
    method =~ /play_(\w+)/ || super
  end
end

p = StereoPlayer.new
p.play_some_Beethoven # => "Here's some_Beethoven"
p.respond_to? :play_some_Beethoven # => true
m = p.method(:play_some_Beethoven) # => #<Method: StereoPlayer#play_some_Beethoven>
# m acts like any other method:
m.call # => "Here's some_Beethoven"
m == p.method(:play_some_Beethoven) # => true
m.name # => :play_some_Beethoven
StereoPlayer.send :define_method, :ludwig, m
p.ludwig # => "Here's some_Beethoven"

ready = ->

  ...your coffeescript goes here...

$(document).ready(ready)
$(document).on('page:load', ready)

var ready;
ready = function() {

  ...your javascript goes here...

};

$(document).ready(ready);
$(document).on('page:load', ready);

Book.where(:title => 'Tale of Two Cities').first_or_create

Book.where(:title => 'Tale of Two Cities').first_or_create do |book|
  book.author = 'Charles Dickens'
  book.published_year = 1859
end

Book.where(:title => 'Tale of Two Cities').first_or_initialize

def geekify(string)
  string.gsub(/[leto]/, 'l' => '1', 'e' => '3', 't' => '7', 'o' => '0')
end

geekify('leet') # => '1337'
geekify('noob') # => 'n00b'

def doctorize(string)
  string.gsub(/M(iste)?r/, 'Mister' => 'Doctor', 'Mr' => 'Dr')
end

doctorize('Mister Freeze') # => 'Doctor Freeze'
doctorize('Mr Smith')   # => 'Dr Smith'

# Index HTML Files
if (-f $document_root/cache/$uri/index.html) {
  rewrite (.*) /caches/$1/index.html break;
}

# HTML Files
if (-f $document_root/cache/$uri.html) {
  rewrite (.*) /caches/$1.html break;
}

# Catch all
if (-f $document_root/cache/$uri) {
  rewrite (.*) /caches/$1 break;
}

class Object 
  def tap 
    yield self 
    self 
  end 
end

blah.sort.grep( /foo/ ).map { |x| x.blah }

xs = blah.sort.grep( /foo/ )
p xs

# do whatever we had been doing with the original expression
xs.map { |x| x.blah }

blah.sort.grep( /foo/ ).tap { |xs| p xs }.map { |x| x.blah }

def index
  @recipe_collection = RecipeCollection.from_params(params)
  render json: @recipe_collection.recipes
end

class RecipeCollection
  attr_accessor :featured, :time_filter

  # Handles the logic of sorting params into a collection
  def self.from_params(params)
    RecipeCollection.new.tap do |recipe_collection|
      recipe_collection.time_filter = params[:time_filter]
      recipe_collection.featured = params[:featured]
    end
  end

  # Should return an ActiveRecord relation
  def recipes
    query = Recipe.scoped
    query.featured if featured.present?
    query.filter_by_time(time_filter)
  end

  def time_filter
  valid_time_filters.include?( @time_filter ) ? @time_filter : default_time_filter
  end

  def default_time_filter
    "today"
  end

  def valid_time_filters
    %w[ today yesterday this-week this-year ]
  end
end

<%- if current_user.redesign_enabled? %>
  <%# new code %>
<%- else %>
  <%# old code %>
<%- end %>

class ApplicationController < ActionController::Base
  before_filter :add_view_path_for_redesign

  private

  def add_view_path_for_redesign
    if current_user.redesign_enabled?
      prepend_view_path Rails.root.join('app/views/redesign')
    end
  end
end

# original
app/views/users/edit.html.erb
app/views/users/show.html.erb

# redesign
app/views/redesign/users/edit.html.erb
app/views/redesign/users/show.html.erb