# Nuances of alias\_method

**URL:** <https://www.ruby-forum.com/t/nuances-of-alias-method/186810>\
**Category:** Ruby\
**Created:** [April 12, 2010, 7:08pm UTC](https://www.ruby-forum.com/t/nuances-of-alias-method/186810 "2010-04-12T19:08:33Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![rjlyders](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/58f4c7/32.png) [@rjlyders](https://www.ruby-forum.com/u/rjlyders)\
**Post date:** [April 12, 2010, 7:08pm UTC](https://www.ruby-forum.com/t/nuances-of-alias-method/186810/1 "2010-04-12T19:08:33Z")

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I am stumbling around some of the nuances of Ruby classes, especially in  
regard to alias\_method. Specifically, can someone explain to me why this  
doesn’t work:

class A  
def A.foo  
“Hello”  
end  
end

A.send(:alias\_method, :bar, :foo) # =\> NameError: undefined method  
`foo' for class`A’

But this does:

class A  
def A.foo  
“Hello”  
end  
end

class \<\< A  
alias\_method :bar, :foo  
end

A.foo # =\> Hello  
A.bar # =\> Hello

---

<div class="post-metadata">

**Author:** ![rjlyders](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/58f4c7/32.png) [@rjlyders](https://www.ruby-forum.com/u/rjlyders)\
**Post date:** [April 12, 2010, 7:41pm UTC](https://www.ruby-forum.com/t/nuances-of-alias-method/186810/2 "2010-04-12T19:41:52Z")

</div>

On Mon, Apr 12, 2010 at 7:08 PM, Richard L. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> A.send(:alias\_method, :bar, :foo) # =\> NameError: undefined method  
> class \<\< A  
> alias\_method :bar, :foo  
> end
> 
> ## A.foo # =\> Hello A.bar # =\> Hello
> 
> Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/).

Well alias\_method aliases instance methods, as foo is not an instance  
method of class A it cannot be aliased there. But as foo is an  
instance method of the singleton class of A (class \<\< A) it can be  
aliased there.  
IOW  
class A  
def foo; 42 end  
end  
now foo is an instance method of A and not of (class \<\< A) and thus  
your A.send…  
would work, as would  
A.module\_eval do  
alias\_

or  
class A  
alias\_…  
end

HTH  
Robert