Ruby Class Variable Examples without @@

class_variable_example.rb

# Ruby Class Variable Examples without @@
# http://www.sitepoint.com/class-variables-a-ruby-gotcha/

class Foo
  def self.talk
    puts 'Hey! I\'m talking'
  end
end

class Bar
  def run!
    Foo.talk
  end
end

puts '-' * 150
puts '[Bar]'
Bar.new.run!

class BarWithInjection
  @@foo_klass = nil

  def initialize(foo_klass)
    @foo_klass = foo_klass
  end

  def run!
    @foo_klass.talk
  end
end

puts '-' * 150
puts '[BarWithInjection]'
BarWithInjection.new(Foo).run!

class BarWithExternalInjection
  class << self
    attr_accessor :foo_klass
  end

  def self.set_foo_class(klass)
    @foo_klass = klass
  end

  def self.run!
    @foo_klass.talk
  end

  def instance_run!
    self.class.foo_klass.talk
  end
end

puts '-' * 150
puts '[BarWithExternalInjection]'
BarWithExternalInjection.set_foo_class(Foo)
BarWithExternalInjection.run!
BarWithExternalInjection.foo_klass

puts '.' * 150

puts '[BarWithExternalInjection] INSTANCE'
BarWithExternalInjection.new.instance_run!

puts '-' * 150