Scopes behavior in ActiveRecord 4

README.md

Example of interesting behavior of scopes in ActiveRecord 4.

● master ~/Code/OSS/scope-v-method » bundle console
irb(main):001:0> require_relative 'foo'
=> true
irb(main):002:0> Foo.bar
=> [:bar]
irb(main):003:0> _.class
=> Array
irb(main):004:0> Foo.baz
=> #<ActiveRecord::Relation []>
irb(main):005:0> _.class
=> Foo::ActiveRecord_Relation
irb(main):006:0> Foo.create! name: 'foo'
=> #<Foo id: 1, name: "foo">
irb(main):007:0> Foo.by_name_s('foo')
=> ["foo"]
irb(main):008:0> _.class
=> Array
irb(main):009:0> Foo.by_name_m('foo')
=> ["foo"]
irb(main):010:0> _.class
=> Array

Also see the same example in ActiveRecord 3

foo.rb

require 'active_record'

class Foo < ActiveRecord::Base
  establish_connection adapter: 'sqlite3', database: ':memory:'

  connection.create_table :foos do |t|
    t.string :name
  end

  scope :bar, ->() do
    [:bar]
  end

  scope :baz, ->(){}

  scope :by_name_s, ->(name) do
    scoped = where(name: name)
    scoped.map(&:name)
  end

  def self.by_name_m(name)
    scoped = where(name: name)
    scoped.map(&:name)
  end
end

Gemfile

source 'https://rubygems.org'

gem 'activerecord', '~>4.0'
gem 'sqlite3'

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    activemodel (4.1.6)
      activesupport (= 4.1.6)
      builder (~> 3.1)
    activerecord (4.1.6)
      activemodel (= 4.1.6)
      activesupport (= 4.1.6)
      arel (~> 5.0.0)
    activesupport (4.1.6)
      i18n (~> 0.6, >= 0.6.9)
      json (~> 1.7, >= 1.7.7)
      minitest (~> 5.1)
      thread_safe (~> 0.1)
      tzinfo (~> 1.1)
    arel (5.0.1.20140414130214)
    builder (3.2.2)
    i18n (0.6.11)
    json (1.8.1)
    minitest (5.4.1)
    sqlite3 (1.3.9)
    thread_safe (0.3.4)
    tzinfo (1.2.2)
      thread_safe (~> 0.1)

PLATFORMS
  ruby

DEPENDENCIES
  activerecord (~> 4.0)
  sqlite3