From: matt@... (matt neuburg)
Date: 2009-03-15T03:37:46+09:00
Subject: Re: Problem With eval and each_index

Christopher Dicely <cmdicely@gmail.com> wrote:

> On Fri, Mar 13, 2009 at 7:32 PM, matt neuburg <matt@tidbits.com> wrote:
> > Michael W. Ryder <_mwryder@worldnet.att.net> wrote:
> >
> >> I am trying to set a group of variables to values stored in a tab
> >> delimited string.  I have no problem splitting the string into an array,
> >> call it e, or in putting the variable names in a second array, call it
> >> v.  The problem arises when I try to merge the two together.  If I enter:
> >> irb(main):073:0> p v
> >> ["name", "street", "city", "state", "zip", "*", "telephone"]
> >> => nil
> >> irb(main):074:0> p e
> >> ["John Doe", "123 Main St", "Anywhere", "US", "01234-5678", "ab123",
> >> "1234567890"]
> >> => nil
> >> irb(main):075:0> eval "#{v[0]} = e[0]"
> >> => "John Doe"
> >> irb(main):076:0> p name
> >> "John Doe"
> >> => nil
> >>
> >> it works as I want.  But when I try:
> >> irb(main):077:0> v.each_index {|i| eval "#{v[i]} = e[0]"}
> >> => ["name", "street", "city", "state", "zip", "*", "telephone"]
> >>
> >> and then enter: puts zip
> >> it returns with a NameError saying that the variable was undefined.
> >
> > Inside a block, local variables are local to the block. So, you're
> > creating all those local variables and then the block ends and they are
> > all thrown away.
> >
> > Why do you need variables called "name" (etc.) anyway? Why not use a
> > hash, so that h["name"] contains the name ("John Doe"), h["street"]
> > contains the street, and so on? So:
> >
> > h = Hash.new
> > v.zip(e).each {|k,v| h[k]=v}
> 
> or, better:
> 
> h = Hash[*v.zip(e).flatten]

Right you are, sorry about that. m.

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