From: Tim Pease <tim.pease@...>
Date: 2006-10-24T07:54:08+09:00
Subject: Re: What's the difference between send and instance_eval?

On 10/23/06, michele <michelemendel@gmail.com> wrote:
> What's the difference between send and instance_eval (except the
> obvious syntax)?
>
> I've been trying to figure out why Ruby has them both. It seems you can
> use them intechangeably, at least in the cases I've found and tested
> (so the question is if there is a case where can't change one for the
> other).
>
> Sorry if this has been answered already. I really tried to find the
> answers in my Ruby and Rails books and on the Internet before posting
> the question here.
>

send can only be used to execute existing methods on objects.

instance_eval allows you to do much more -- i.e. adding instance
variables, tinkering with private methods, etc

ary = %w( 1 2 3 4 )

ary.send :length               #=> 4

ary.instance_eval do
  @length = self.length
end

ary.instance_variable_get :@length        #=> 4


It's a dumb example, but it should convery the differences.

Blessings,
TwP