From: Mason Kelsey <masonkelsey@...>
Date: 2009-08-25T10:47:34+09:00
Subject: Re: Ruby eval

--001485f7252e85764e0471ed84bd
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

Others can correct me if I'm wrong, as I'm also new to Ruby.  (My 127th
language.) But eval , which also exist in several other languages, is used
when you need to change a COMMAND dynamically, after the program starts
running and is beyond the reach of the programmer.  Since that is a fairly
complex situation and beyond the need for most programmers, eval should
normally not be used in production systems.  I suspect that eval would be
caught in any production walkthrough by other professional programmers as a
potential security threat, since it would be easy to obscure what the code
is actually doing.  For example, it could be used to create a trap door.  In
that case the programmer would have to rewrite the code without using eval
to comply.  So it is a waste of valuable time in most production systems
development or maintenance to use that command.  I assume that eval in Ruby
is the same thing.  Use eval for experimental or academic stuff, for example
in artificial intelligence.

No Sam

On Mon, Aug 24, 2009 at 3:24 PM, Brandon Larocque
<larocque.brandon@live.ca>wrote:

> I am trying to learn Ruby as a first language, ( I tended to go back and
> forth over languages in my studies, but I plan, now, to focus on Ruby ),
> and came across a confusing problem. My brother likes to play Mafia Wars
> on facebook and asked me to come up with something simple. So I put a
> little something together, and it involved the eval function.
>
> From what I've read, recently, people tend to look down on the eval
> function? Why is this? I have a few classes that have multiple names, so
> I decided to use it to work through the problem I was having ( I didn't
> want to write a bunch of loops ). For example :
>
> ( $jobarea == "hi" or $jobarea == "es" ) ? (loop = 9) : ( ($jobarea ==
> "ca") ? (loop = 8) : (loop = 7) )
> expcost = [] ; exppay = [] ; pay = [] ; name = []
> for i in (1..loop) do
>  eval("expcost.push $#{$jobarea}_job#{i}.expcost")
>  eval("exppay.push $#{$jobarea}_job#{i}.exppay")
>  eval("pay.push $#{$jobarea}_job#{i}.pay")
>  eval("name.push $#{$jobarea}_job#{i}.name")
> end
>
> Is there any way that I might be able to do this without eval? Or is it
> alright the way I have done it?
>
> Regards,
> Brandon LaRocque
> --
> Posted via http://www.ruby-forum.com/.
>
>

--001485f7252e85764e0471ed84bd--