From: Rodrigo Rosenfeld Rosas <rr.rosas@...>
Date: 2011-01-20T23:28:04+09:00
Subject: [ruby-core:34663] Re: Returning from the callee

  Em 20-01-2011 08:21, Nikolai Weibull escreveu:
> 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

I was trying to be concise, but I guess it wasn't a good idea. Let me 
put this way:

def update
     ...
     render text: 'invalid' unless @m.valid?
     # Several lines of code here if the request is valid
     render text: 'valid'
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.)

I'll reply to that comment suggesting this approach later. (I'm a little 
bit in a hurry right now)

Best regards, Rodrigo.