From: dblack@...
Date: 2007-08-03T02:32:15+09:00
Subject: Re: binding - how to explain it?

Hi --

On Fri, 3 Aug 2007, Giles Bowkett wrote:

> There was a thread here recently about this idiom in Rails:
>
> eval(IO.read(file), binding, file)
>
> I changed it to a method:
>
> def eval_file_with_binding(file)
>  eval(IO.read(file), binding, file)
> end
>
> It appeared twice in Rails, so refactoring it was kind of overkill,
> but I have code OCD. Plus, the thread on this list came from somebody
> trying to puzzle out what the code did, and it's very repetitive code,
> so I wanted to make it simpler and clearer.
>
> Anyway, the tests pass, but the patch hasn't been applied, because
> there's a question raised, which is why does it send the correct
> binding when it's defined in some other method. On the one hand the
> answer seems obvious, because it's a method on Kernel, but honestly I
> can't understand it as well as I think I do, because I can't explain
> it beyond that "obvious" point. How do I explain how this code works?
> How does this code work? I know it works, but I can't actually explain
> it.

Can you produce a complete working example?  I'm having trouble
getting it not to not work....  Here's what I'm doing so far:

a = 1

def x
   eval(DATA.read, binding)
end

x    # error: a undefined

__END__
puts a


Is that analogous to what's in the original?


David

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