Scopes behavior in ActiveRecord 3

README.md

Example of interesting behavior of scopes in ActiveRecord 3.

● master ~/Code/OSS/scope-v-method » bundle console
Resolving dependencies...
irb(main):001:0> require_relative 'foo'
=> true
irb(main):002:0> Foo.bar
=> []
irb(main):003:0> _.class
=> Array
irb(main):004:0> Foo.baz
=> []
irb(main):005:0> _.class
=> ActiveRecord::Relation
irb(main):006:0> Foo.create! name: 'foo'
=> #<Foo id: 1, name: "foo">
irb(main):007:0> Foo.by_name_s('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 4

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', '~>3.0'
gem 'sqlite3'

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    activemodel (3.2.19)
      activesupport (= 3.2.19)
      builder (~> 3.0.0)
    activerecord (3.2.19)
      activemodel (= 3.2.19)
      activesupport (= 3.2.19)
      arel (~> 3.0.2)
      tzinfo (~> 0.3.29)
    activesupport (3.2.19)
      i18n (~> 0.6, >= 0.6.4)
      multi_json (~> 1.0)
    arel (3.0.3)
    builder (3.0.4)
    i18n (0.6.11)
    multi_json (1.10.1)
    sqlite3 (1.3.9)
    tzinfo (0.3.41)

PLATFORMS
  ruby

DEPENDENCIES
  activerecord (~> 3.0)
  sqlite3