From: Nikolai Weibull <now@...>
Date: 2011-01-20T19:21:33+09:00
Subject: [ruby-core:34653] Re: Returning from the callee

On Thu, Jan 20, 2011 at 02:00, Rodrigo Rosenfeld Rosas
<rr.rosas@gmail.com> wrote:
> Sometimes it is useful to be able to return from the callee method. For
> instance, consider a web application (how innovative, this is, right?):

> def update
> ������ @m = Model.find(params[:id])
> ������ @m.attributes = params[:model]
> ������ render text: 'invalid' unless @m.valid?
> ������ render text: 'valid'
> end
>
> The experienced Rails user will know this will raise a DoubleRenderError
> exception (in Grails it would be worse, since no exception would be raised
> but the results would be concatenated).
>
> That is because, although we expect that "render" is the last thing to
> happen while dealing with web requests, render cannot return from the callee
> currently in Ruby. I guess Rails would implement it that way if this was
> allowed in Ruby.

Can you please provide a more elaborate example?  I can���t deduce the
value of your proposal from it.  Your example is just a convoluted
version of

def update
  ���
  render text: @m.valid? ? 'valid' : 'invalid'
end

(It���s not very localization-friendly either, but that���s another story ;-).

(And, as already suggested, non-local exits are probably better
controlled with catch/throw.)