From: Robert Dober <robert.dober@...>
Date: 2006-11-12T18:01:54+09:00
Subject: Re: eval question

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On 11/11/06, Peter Szinek <peter@rubyrailways.com> wrote:
>
> Hi,
>
> I am setting up a few variables based on user input with the following
> code snippet:
>
> ==================================
> vars = %w{a b c}
>
> vars.each do |var|
>   print "#{var} = "
>   val = gets
>   eval("$#{var}=#{val.chomp}")
> end
>
> #use a, b, c here for something
> ==================================
>
> What I don't like about this code is the use of global variables.
> However, I have to use them - or otherwise a,b,c will be already out of
> scope at the place I need them.
>
> Another possibility would be to use constants, i.e.
>
> vars = %w{A B C}
>
> which would work well - however, since I am repeating the process more
> times, from the second iteration on I am getting warnings that A, B, C
> etc were already initialized, which is not nice.
>
> I guess yet another possibility would be to wrap a class around this
> stuff and use instance_eval or something like that - but a class that
> serves solely this purpose looks to heavy to me...
>
> Any other ideas?
>
> TIA,
> Peter


Just two tiny improvements
* Do not use globals
* Do not use eval
#!/usr/bin/ruby

vars = %w{a b c}

vars.each do |var|
    print "#{var} = "
    val = gets.chomp
    instance_variable_set "@#{var}", val
end


puts "a = #{@a}"

Maybe you prefer this?
But if you want to access the instance variables by name you can also define
an attribute_reader/writer/accessor inside the vars.each loop.



Cheers
Robert

__
> http://www.rubyrailways.com
>
>


-- 
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore all progress
depends on the unreasonable man.

- George Bernard Shaw

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