From: Robert Klemme <shortcutter@...>
Date: 2010-11-26T20:43:44+09:00
Subject: Re: instance_eval vs attr_reader

On Fri, Nov 26, 2010 at 12:25 PM, Joe Pikachu <nahpr@yahoo.com> wrote:
> Thanks for everyone who replied. I MADE A MISTAKE IN MY ORIGINAL
> EXAMPLE.
> What I meant to compare speed/memory wise was:
>
> my_class.instance_eval {@var} vs. #NOT my_class.instance_eval(@var)
> my_class.var #using attr_reader
>
> So the 'argument' is a block. Does it make any difference at all. What I
> understand is that by using instance_eval self becomes my_class and one
> can access the variable. This seems to my much easier that having to add
> a
> attr_reader-line-of-code every time one needs to access a variable from
> outside. But is it practical, in the long run?

Most Ruby programs use that approach.

> @Stefano Crocco: With the new example @var none-string works.
> @Robert Klemme: I can't use Benchmark at the moment.

Why?  It's not difficult:

12:40:07 ~$ ruby19 -r benchmark <<CODE
> T = 10000
> Benchmark.bm 10 do |x|
> x.report("foo") { T.times { 1 + 2 } }
> x.report("bar") { T.times { 1 * 2 } }
> end
> CODE
                user     system      total        real
foo         0.000000   0.000000   0.000000 (  0.002000)
bar         0.000000   0.000000   0.000000 (  0.002000)
12:41:04 ~$

Replace "1+2" and "1*2" with the code you want to compare.  Of course,
you can put this in a script.

Again, stop wondering, start measuring.

> @Phillip Gawlowski: If I'm not mistaken, symblos are NEVER G.collected.
> That's my concern. Since I'm making dozen of symbols. Also, can you give
> me a good link on how memory/speed works in computer programming. I use
> google, but I don't think I'm using the right keywords.

"Dozens" is not actually what I would call "many".  Don't worry.

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/