Rails - Aug 2005 - Redirection in superclass before filter: DoubleRenderError

In edit forms I''m providing buttons to move from the currently edited 
object to the first, previous, next, last object in the list of 
recently found objects. The actions are represented as an additional 
request parameter, nav. In my controller superclass I have a method, 
navigation_redirect (see bottom), that interprets this parameter and 
redirects to the appropriate URL.

When I install a before filter in a concrete controller like this

    prepend_before_filter :navigation_redirect

it works. When I push this filter to the superclass, I get a 
DoubleRenderError, blamed on the redirect_to at the bottom of the 
method. Frankly, I don''t understand what the difference is between 
these two cases.

Michael


    def navigation_redirect
      current_id = params[:id].to_i
      if (where = params[:nav]) && (navigation_list = 
session[''navigation_list''])
        redirect_to_id           case where
          when ''first''
            navigation_list.first
          when ''last''
            navigation_list.last
          when ''prev''
            idx = navigation_list.index(current_id) || 1
            navigation_list[idx - 1]
          when ''next''
            idx = navigation_list.index(current_id) || -1
            idx = -1 if idx >= navigation_list.length - 1
            navigation_list[idx + 1]
          end
      end
      if redirect_to_id
        redirect_to :id => redirect_to_id
      end
    end


-- 
Michael Schuerig                 Nothing is as brilliantly adaptive
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org       as selective
stupidity.
http://www.schuerig.de/michael/    --A.O. Rorty, The Deceptive Self

Instead of:

prepend_before_filter :navigation_redirect

Try:

prepend_before_filter :navigation_redirect and return

The before_filter redirect doesn''t stop the rest of the action from
being
carried out, so you may end up calling redirect/render again somewhere in
the action, and that''s causing an error.

- Aaron ''Jomdom'' Ransley
- Web: www.jomdom.net
- Mail: jomdom-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org 

-----Original Message-----
From: rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
[mailto:rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org] On
Behalf Of Michael Schuerig
Sent: Monday, August 08, 2005 1:45 PM
To: rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
Subject: [Rails] Redirection in superclass before filter: DoubleRenderError


In edit forms I''m providing buttons to move from the currently edited 
object to the first, previous, next, last object in the list of 
recently found objects. The actions are represented as an additional 
request parameter, nav. In my controller superclass I have a method, 
navigation_redirect (see bottom), that interprets this parameter and 
redirects to the appropriate URL.

When I install a before filter in a concrete controller like this

    prepend_before_filter :navigation_redirect

it works. When I push this filter to the superclass, I get a 
DoubleRenderError, blamed on the redirect_to at the bottom of the 
method. Frankly, I don''t understand what the difference is between 
these two cases.

Michael


    def navigation_redirect
      current_id = params[:id].to_i
      if (where = params[:nav]) && (navigation_list = 
session[''navigation_list''])
        redirect_to_id           case where
          when ''first''
            navigation_list.first
          when ''last''
            navigation_list.last
          when ''prev''
            idx = navigation_list.index(current_id) || 1
            navigation_list[idx - 1]
          when ''next''
            idx = navigation_list.index(current_id) || -1
            idx = -1 if idx >= navigation_list.length - 1
            navigation_list[idx + 1]
          end
      end
      if redirect_to_id
        redirect_to :id => redirect_to_id
      end
    end


-- 
Michael Schuerig                 Nothing is as brilliantly adaptive
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org       as selective
stupidity.
http://www.schuerig.de/michael/    --A.O. Rorty, The Deceptive Self
_______________________________________________
Rails mailing list
Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
http://lists.rubyonrails.org/mailman/listinfo/rails

On Tuesday 09 August 2005 00:48, Aaron ''Jomdom'' Ransley
wrote:
> Instead of:
>
> prepend_before_filter :navigation_redirect
>
> Try:
>
> prepend_before_filter :navigation_redirect and return
>
> The before_filter redirect doesn''t stop the rest of the action
from
> being carried out, so you may end up calling redirect/render again
> somewhere in the action, and that''s causing an error.
No, that''s not the cause. Apparently I''ve misled you, though.
I''m not
calling prepend_before_filter from within a method, it''s at the top of 
the class definition.

Michael

-- 
Michael Schuerig                 Not only does lightning not strike
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org       twice, it usually
doesn''t strike once.
http://www.schuerig.de/michael/  --Salman Rushdie, Fury

Did you give it a shot, none the less? I had a lot of such errors when I
changed from 0.12 to 0.13, and doing the ''and return'' on the
end of my
filters helped in a lot of cases.

- Aaron ''Jomdom'' Ransley
- Web: www.jomdom.net
- Mail: jomdom-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org 

-----Original Message-----
From: rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
[mailto:rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org] On
Behalf Of Michael Schuerig
Sent: Monday, August 08, 2005 3:53 PM
To: rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
Subject: [Rails] Re: Redirection in superclass before
filter:DoubleRenderError

On Tuesday 09 August 2005 00:48, Aaron ''Jomdom'' Ransley
wrote:
> Instead of:
>
> prepend_before_filter :navigation_redirect
>
> Try:
>
> prepend_before_filter :navigation_redirect and return
>
> The before_filter redirect doesn''t stop the rest of the action
from
> being carried out, so you may end up calling redirect/render again
> somewhere in the action, and that''s causing an error.
No, that''s not the cause. Apparently I''ve misled you, though.
I''m not
calling prepend_before_filter from within a method, it''s at the top of 
the class definition.

Michael

-- 
Michael Schuerig                 Not only does lightning not strike
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org       twice, it usually
doesn''t strike once.
http://www.schuerig.de/michael/  --Salman Rushdie, Fury
_______________________________________________
Rails mailing list
Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
http://lists.rubyonrails.org/mailman/listinfo/rails

On Tuesday 09 August 2005 00:58, Aaron ''Jomdom'' Ransley
wrote:
> Did you give it a shot, none the less? I had a lot of such errors
> when I changed from 0.12 to 0.13, and doing the ''and
return'' on the
> end of my filters helped in a lot of cases.
Yes, I just did. The error must in some way be related to the class 
hierarchy. Remember, when I prepend the before filter in the concrete 
controller class it works. The error occurs only if I push the prepend 
the filter in my superclass.

Michael

-- 
Michael Schuerig                  I am the sum total of the parts
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org        I control
directly.
http://www.schuerig.de/michael/   --Daniel C. Dennett, Elbow Room

On Tuesday 09 August 2005 01:09, Michael Schuerig wrote:
> On Tuesday 09 August 2005 00:58, Aaron ''Jomdom'' Ransley
wrote:
> > Did you give it a shot, none the less? I had a lot of such errors
> > when I changed from 0.12 to 0.13, and doing the ''and
return'' on the
> > end of my filters helped in a lot of cases.
>
> Yes, I just did. The error must in some way be related to the class
> hierarchy. Remember, when I prepend the before filter in the concrete
> controller class it works. The error occurs only if I push the
> prepend the filter in my superclass.
I found the cause. When running in the development environment, filters 
defined in a superclass are executed for each class in the inheritance 
hierarchy downward.

Reported as <http://dev.rubyonrails.org/ticket/1927>

Michael

-- 
Michael Schuerig                  Failures to use one''s frontal lobes
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org        can result in the
loss of them.
http://www.schuerig.de/michael/   --William H. Calvin