Ruby Protected vs Private

ruby_protected_vs_private.rb

class Parent
  def public_foo
    "public foo"
  end
  
  protected
  
  def pro_foo
    "protected foo"
  end
  
  private
  
  def priv_foo
    "private foo"
  end
end

class Child < Parent
  def priv_foo
    priv_foo
  end
  
  def pro_foo_of(a)
    a.pro_foo
  end
  
  def priv_foo_of(a)
    a.priv_foo
  end
end

parent = Parent.new
parent.pro_foo # NoMethodError: protected method `pro_foo`

child = Child.new
child.priv_foo # => "private foo"
child.pro_foo_of(parent) #=> "protected foo"
child.priv_foo_of(parent) #=> # NoMethodError: protected method `pro_foo`

# Ref: http://stackoverflow.com/questions/9882754/what-are-the-differences-between-private-public-and-protected-methods