From: Rick DeNatale <rick.denatale@...>
Date: 2006-10-27T00:24:47+09:00
Subject: Re: What's the difference between send and instance_eval?

On 10/26/06, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:

> That's true, but only because I chose a bad example. Here's a better one:
>
> h = {1=>2}
> msg = [:concat, [4, 5, 6, IO, String, Kernel, h]]
> a = [1,2,3]
> p a.send(*msg)   # ==> [1, 2, 3, 4, 5, 6, IO, String, Kernel, {1=>2}]
> p a.instance_eval(msg.to_s) # ==> NameError
>
> To make the instance_eval work here, you would have to find a way to
> turn the argument array into a string that, when eval-ed, is that same
> array. (It's possible, but painful, and you lose the identity of the
> hash h.)

except that instance_eval can take a block in lieu of a string:

a.instance_eval {concat [1,2,3,4,5,6,IO,String,Kernel, h]}
=> [1, 2, 3, 1, 2, 3, 4, 5, 6, IO, String, Kernel, {1=>2}]

Not that I think that send should be eliminated, both methods are
useful. Horses for courses.

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/