From: apeiros <apeiros@...>
Date: 2009-06-17T05:47:26+09:00
Subject: [ruby-core:23879] Re: instance_eval no longer yielding self in ruby  1.9

Am 16.06.2009 um 22:12 schrieb Yusuke ENDOH:
> Hi,
>
> 2009/6/14 apeiros <apeiros@gmx.net>:
>> Hi folks
>>
>> In ruby 1.8, instance_eval yielded self, this is no longer the case  
>> in ruby
>> 1.9.
>> Was this an informed decision or just an oversight (after all it was
>> undocumented in 1.8)?
>> If it was an informed decision I'd be interested in the rationale.
>
> matz's decision.  [ruby-core:7365]

Ah, interesting, thank you.

> The rationale seems to be arguable...

Indeed :)

>> It was nice for blocks that didn't care whether they were  
>> instance_eval'd or
>> just called/yielded to, as long as they get an argument. With 1.9  
>> those
>> blocks have to be written specifically for instance_eval and use self
>> instead of the argument.
>
> You can use Object#instance_exec for the purpose.

So I define the method conditionally like:
   if method_defined? :instance_exec then
     def ...; instance_exec(self, &block); ...; end
   else
     def ...; instance_eval(&block); ...; end
   end

?

I don't know, but I find that solution somewhat ugly. The alternative  
is to have no 1.8 compatibility which is right now not too nice.

Regards
Stefan Rusterholz