From: Todd Benson <caduceass@...>
Date: 2008-02-22T05:04:16+09:00
Subject: Re: Where does instance_eval _magically_ set the variable to?

On Thu, Feb 21, 2008 at 1:44 PM, Andrew Chen <hangfei@gmail.com> wrote:
> Hi,
>
>  I use the instance_eval to merge template file and parameter files.
>
>   >cat param.txt
>  name="John"
>   >cat tmpl.txt
>  my name is: <%= name %>
>
>   >cat template.rb
>  #!/usr/bin/env ruby
>  require 'erb'
>

name = nil

>  instance_eval(File.read('param.txt'))
>  puts ERB.new(File.read("tmpl.txt")).result(binding)
>
>  puts name
>
>   >template.rb
>  my name is: John
>  template.rb:7: undefined method `name' for main:Object (NoMethodError)
>
>
>  Where is the variable "name" set to?  How to access it?
>  It must be somewhere, since it is used in the tmpl.txt file.
>
>  Is there any "magic" namespace in Ruby?

It's just a scope issue.  If you use name = nil like I did above you
should be okay.  I wonder, though, why you would want to
#instance_eval instead of using #load.

Also, some rubyists advocate using the block method of File.open as
well.  I'm not sure if File.read closes the file automatically.

hth,
Todd