The difference between Ruby alias and alias_method

#ruby #ticks

In some open source ruby projects you may see similar alias and alias_method methods. what are the specific use of these two methods? how are these two methods different? let's look at the following code:

#alias
class User
  def full_name
    puts "Mixbo"
  end
  alias name full_name
end
User.new.name #=>Mixbo

#alias_method
class User
  def full_name
    puts "Mixbo"
  end
  alias_method :name, :full_name
end
User.new.name #=> Mixbo

The above examples all output the "Mixbo" string before renaming the full_name in the User class. from this example alone we can't see the difference between the two methods continue:

#alias_method
class User
  def full_name
    puts "Super Mixbo"
  end
  def self.rename
    alias_method :name, :full_name #==> Note that alias_method is used here
  end
end

class Mixbo < User
  def full_name
    puts "Mixbooooo"
  end
  rename
end
Mixbo.new.full_name #=> "Mixbooooo"


#alias
class User
  def full_name
    puts "Super Mixbo"
  end
  def self.rename
    alias :name :full_name #==> Note that alias is used here
  end
end

class Mixbo < User
  def full_name
    puts "Mixbooooo"
  end
  rename
end
Mixbo.new.name #=> 'Super Mixbo'

From the above example we can see that when there is an inheritance relationship between classes. alias will not affect its subclasses. related alias_method will find the closest method of the same name in its subclass to operate (for example, full_name above)