Should I use alias or alias_method?

Question

I found a blog post on alias vs. alias_method. As shown in the example given in that blog post, I simply want to alias a method to another within the same class. Which should I use? I always see alias used, but someone told me alias_method is better.

Usage of alias

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

Usage of alias_method

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

Blog post link here

Answer 1

alias_method can be redefined if need be. (it's defined in the Module class.)

alias's behavior changes depending on its scope and can be quite unpredictable at times.

Verdict: Use alias_method - it gives you a ton more flexibility.

Usage:

def foo   "foo" end  alias_method :baz, :foo 

Answer 2

Apart from the syntax, the main difference is in the scoping:

# scoping with alias_method class User    def full_name     puts "Johnnie Walker"   end    def self.add_rename     alias_method :name, :full_name   end  end  class Developer < User   def full_name     puts "Geeky geek"   end   add_rename end  Developer.new.name #=> 'Geeky geek' 

In the above case method “name” picks the method “full_name” defined in “Developer” class. Now lets try with alias.

class User    def full_name     puts "Johnnie Walker"   end    def self.add_rename     alias name full_name   end end  class Developer < User   def full_name     puts "Geeky geek"   end   add_rename end  Developer.new.name #=> 'Johnnie Walker' 

With the usage of alias the method “name” is not able to pick the method “full_name” defined in Developer.

This is because alias is a keyword and it is lexically scoped. It means it treats self as the value of self at the time the source code was read . In contrast alias_method treats self as the value determined at the run time.

Source: http://blog.bigbinary.com/2012/01/08/alias-vs-alias-method.html