From: Jacob Fugal <lukfugl@...>
Date: 2005-07-20T03:31:07+09:00
Subject: Re: Instance Eval of a Proc

On 7/19/05, Daniel Brockman <daniel@brockman.se> wrote:
> "Ara.T.Howard" <Ara.T.Howard@noaa.gov> writes:
> 
> > the behaviour of Foo.method(:show_name) does exactly as
> > advertised - binding the method to the class Foo along
> > with that notion of self and instance vars.
> 
> That is not in dispute.
> 
> > so the binding of self for the duration of instance_eval
> > is definitely working
> 
> Wait, wait, wait... timeout!
> 
> Isn't the whole point of 'instance_eval' to change the
> binding of 'self'?

Indeed. "Fighting ri with ri", we have from ri Object#instance_eval:

     Evaluates a string containing Ruby source code, or the given block,
     within the context of the receiver (_obj_). In order to set the
     context, the variable +self+ is set to _obj_ while the code is
     executing, giving the code access to _obj_'s instance variables.

So, according to documentation, instance_eval should set +self+ to
_obj_ while the code is executing. However, this binding doesn't
happen if there's already a binding for self. Question is, should it?
If so, there's a bug. If not, the documentation needs to reflect that.

Jacob Fugal