When do you use method aliasing?

Question

Do you use the alias method in order to add more ways to call methods (like length and size) or is there another use for it?

Answer 1

The alias_method call is also useful for re-implementing something but preserving the original version. There's also alias_method_chain from Rails which makes that kind of thing even easier.

alias_method also comes in handy when you have a number of behaviors that are initially identical but might diverge in the future, where you can at least rough them in to start.

def handle_default_situation
  nil
end

%w[ poll push foo ].each do |type|
  alias_method :"handle_#{type}_situation", :handle_default_situation
end

Answer 2

Yes.

It is often used to preserve a handle to existing methods before overriding them. (contrived example)

Given a class like this:

class Foo
  def do_something
    puts "something"
  end
end

You could see code that adds new behaviour like so:

class Foo
  def do_something_with_logging
    puts "started doing something"
    do_something_without_logging # call original implementation
    puts "stopped doing something"
  end

  alias_method :do_something_without_logging, :do_something
  alias_method :do_something, :do_something_with_logging
end

(this is exactly how alias_method_chain works)

However, for this use case it't often more appropriate to use inheritance and modules to your advantage.

Still, alias_method is a useful tool to have, if you absolutely need to redefine behaviour in an existing class (or if you wanted to implement something like alias_method_chain)