From: Eli Bendersky <eliben@...>
Date: 2006-05-13T01:02:12+09:00
Subject: Re: Making sense of the various Ruby "eval"s

ts wrote:
>>>>>> "E" == Eli Bendersky <eliben@gmail.com> writes:
> 
> E> - Kernel#eval -
> 
>  it's the evil eval, forget it :-)

Forget Kernel#eval or the string version of any #eval ? The first maybe, 
but the second is what allows code generation on-the-fly.

> 
> E> - Object#instance_eval -
> 
> E> Is obj.instance_eval("blah") exactly the same as eval("blah", obj) ?
> 
>  You can give only a Proc/Binding to the evil eval
> 
> E> work ? Are the contents of the block just treated as a string ?
> 
>  no, the block is executed with self = object

And in the string version, what is 'self' ?
I'm struggling to fully understand the difference between the block and 
the string versions ?

> 
> E> - Module#class_eval -
> 
> 
> moulon% cat b.rb
> #!/usr/bin/ruby
> class A
> end
> 
<snip>

OK I think I understand: instance_eval adds instance methods to a class, 
and class/module_eval adds class methods to a class. But also 
instance_eval can be called on any object, but class_eval can't (it can 
be called only on class / module objects). Correct ?



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