Nuances of alias_method

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 classA’

But this does:

class A
def A.foo
“Hello”
end
end

class << A
alias_method :bar, :foo
end

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

On Mon, Apr 12, 2010 at 7:08 PM, Richard L. [email protected]
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/.

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

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs