Rails - Jul 2010 - `stack level too deep` when overwriting `to_json`

I''m using
[acts_as_commentable_with_threading](http://github.com/elight/acts_as_commentable_with_threading/),
and it worked fine until I tried to overwrite the to_json function to
include more details about the associated user.

Here''s part of the comment class (which was originally defined in the
plugin, but I moved it to the models folder, a move which seems not to
affect the error):

    def to_json(options = {})
      {
        :id => id,
        :body => body,
        :parent_id => parent_id,
        :created_at => created_at,
        :updated_at => updated_at,
        :user => user ### the line in question
      }.to_json(options)
    end

When the line is included, the server responds accordingly the first
time you request the resource, but every subsequent request (a
particular oddity), I get:

SystemStackError (stack level too deep):
  app/models/comment.rb:21:in `to_json''
  C:1:in `__send__''
  C:1:in `encode''
  C:1:in `__send__''
  C:1:in `encode''
  app/models/item.rb:61:in `to_json''
  app/controllers/items_controller.rb:20
  app/controllers/items_controller.rb:18:in `show''
  C:/Ruby/lib/ruby/1.8/webrick/httpserver.rb:104:in `service''
  C:/Ruby/lib/ruby/1.8/webrick/httpserver.rb:65:in `run''
  C:/Ruby/lib/ruby/1.8/webrick/server.rb:173:in `start_thread''
  C:/Ruby/lib/ruby/1.8/webrick/server.rb:162:in `start''
  C:/Ruby/lib/ruby/1.8/webrick/server.rb:162:in `start_thread''
  C:/Ruby/lib/ruby/1.8/webrick/server.rb:95:in `start''
  C:/Ruby/lib/ruby/1.8/webrick/server.rb:92:in `each''
  C:/Ruby/lib/ruby/1.8/webrick/server.rb:92:in `start''
  C:/Ruby/lib/ruby/1.8/webrick/server.rb:23:in `start''
  C:/Ruby/lib/ruby/1.8/webrick/server.rb:82:in `start''

Removing the line prevents the error from showing up.

I call associations in to_json elsewhere in the application with no
issues.
-- 
Posted via http://www.ruby-forum.com/.

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

Steven Xu wrote:
>     def to_json(options = {})
>       {
>         :id => id,
>         :body => body,
>         :parent_id => parent_id,
>         :created_at => created_at,
>         :updated_at => updated_at,
>         :user => user ### the line in question
>       }.to_json(options)
>     end
Let''s think about what the call to to_json on the Hash is doing...

Each key/value pair will be sent the message to_json. I assume the Hash 
takes care of providing the JSON representation of the more basic types 
like String, Fixnum, etc. But, what about when to_json gets sent to the 
user object.

Given that Item has_one :user then likely User has_many :items. The item 
your working with may be contained within an array of user, if user''s 
to_json includes items. This might explain how you end up with a "stack 
level too deep."

Since I don''t know how your User model is behaving I can''t say
for sure
that is the problem, but it is something to consider.
-- 
Posted via http://www.ruby-forum.com/.

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

Robert Walker wrote:
> Each key/value pair will be sent the message to_json. I assume the Hash 
> takes care of providing the JSON representation of the more basic types 
> like String, Fixnum, etc. But, what about when to_json gets sent to the 
> user object.
> 
> Given that Item has_one :user then likely User has_many :items. The item 
> your working with may be contained within an array of user, if
user''s
> to_json includes items. This might explain how you end up with a
"stack
> level too deep."
> 
> Since I don''t know how your User model is behaving I
can''t say for sure
> that is the problem, but it is something to consider.
Thanks for the helpful description. I have made that mistake before (not 
with cross-model associations, which are pretty easy to catch, but with 
a nested set when I tried to establish aunt and uncle relationships), 
and I am sure it''s not the case here. Typically, I force jsonning 
associations to be manually declared in the options rather than enable 
them by default, but I did it here because I ruled it out as a cause. 
For the record, the to_json instance method on User doesn''t invoke any 
associations.

I am at a loss of how to troubleshoot this because:

(1) The "works once then fails thereafter" behaviour is really weird.
(2) I can''t reproduce the error through the console (which produces the
expected JSON output, user and all)
-- 
Posted via http://www.ruby-forum.com/.

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

On Jul 14, 10:48 pm, Steven Xu
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> Robert Walker wrote:
> I am at a loss of how to troubleshoot this because:
>
> (1) The "works once then fails thereafter" behaviour is really
weird.
Does it only happen when class caching is turned off ? (don''t forget
to restart the server after you change that)

Fred
> (2) I can''t reproduce the error through the console (which
produces the
> expected JSON output, user and all)
> --
> Posted viahttp://www.ruby-forum.com/.
-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.