From: Stefano Crocco <stefano.crocco@...>
Date: 2008-08-09T05:38:11+09:00
Subject: Re: Inconsistent block parameters handling by instance_eval

On Friday 08 August 2008, Patrick Li wrote:
> class A
>   def A.method &block
>     A.new.instance_eval &block
>   end
>
>   def A.method2 &block
>     A.new.instance_eval {block.call}
>   end
> end
>
> A.method{p self} #prints #<A:0x28c2858>
>
> A.method2{p self} #prints main
>
> From this example: is instance_eval even working in method2? It clearly
> shows that block is not called in A's context.
>   -Patrick

The effect of instance_eval is to set the variable "self" to the receiver for 
the duration of the block. In the first case, everything works as expected. In 
the second case, instead, self is changed only for the outer block, while in 
the inner block "self" remains what it were when the block was defined. 
There's nothing new here: the environment in which the block is executed 
doesn't affect its variables and the fact that instance_eval treats the outer 
block in a special way doesn't otherwise change things.

I hope this helps

Stefano