Rails - Jun 2010 - Why do rails calls a method when I'm calling a property?

Well, I''m starting on RoR, so I got a Book called simply
rails...Following the steps in it sometimes when I try to call a
property, the browser shows me the next exception:

undefined method `name'' for nil:NilClass

I don''t know why...here''s my controller:
#Controller starts here
class StoriesController < ApplicationController
  before_filter :login_required, :only => [ :new, :create]

  def index
    get_stories ''votes_count >= 5''
  end

  def bin
    get_stories ''''
    render :action => ''index''
  end

  protected
  def get_stories(conditions)
    @stories = Story.find :all, :order => ''id DESC'',
:conditions =>
conditions
  end

  def new
    @story = Story.new
  end

  def create
    #@story = Story.new(params[:story])
    @story = @current_user.stories.build params[:story]
    if @story.save
      flash[:notice] = "La historia a sido agregada correctamente!"
      redirect_to stories_path
    else
      render :action => ''new''
    end
  end

  def show
    @story = Story.find_by_id(params[:id])
  end
end
#controller ends here

Here''s my view:
#View starts here
<h2>
   <%= @story.name %>
</h2>
<h3>
    <span id="vote_score">
  Shoveadas => <%= @story.votes.size %>
    </span>
</h3>
<p class="submited_by"> Agregada por: <%= @story.user.login
%> </p>
<p>
    <%= link_to @story.link, @story.link%>
</p>
<div id="vote_form">
  <% form_remote_tag :url => story_votes_path(@story) do %>
    <%= submit_tag ''Shovealo!'' %>
  <% end %>
</div>
<ul id="vote_history">
  <% if @story.votes.empty? %>
    <em>Sin shoveadas aun</em>
  <% else %>
    <%= render :partial => ''votes/vote'', :collection
=> @story.votes %>
  <% end %>
</ul>
#view ends here

From now thank you!
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I would also add that the trouble is in Show view/controller.
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Omar Renteria wrote:
> Well, I''m starting on RoR, so I got a Book called simply
> rails...Following the steps in it sometimes when I try to call a
> property, the browser shows me the next exception:
> 
> undefined method `name'' for nil:NilClass
That''s how Ruby works: all data access is done through method calls. 
Unlike in Java or C++, there is no way (well, except for tricky hacks) 
to see an instance variable from outside the object that contains it. 
This is one of the best features of Ruby, since it means calling 
routines don''t have to know whether they''re asking for an
instance
variable or a computation.

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
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Omar Renteria wrote:
> Well, I''m starting on RoR, so I got a Book called simply
> rails...Following the steps in it sometimes when I try to call a
> property, the browser shows me the next exception:
> 
> undefined method `name'' for nil:NilClass
That''s how Ruby works: all data access is done through method calls.
Unlike in Java or C++, there is no way (well, except for tricky hacks)
to see an instance variable from outside the object that contains it.
This is one of the best features of Ruby, since it means calling
routines don''t have to know whether they''re asking for an
instance
variable or a computation.

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
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If you look at the error "undefined method `name'' for
nil:NilClass,"
it tells you that the error is from attempting to call a method
''name''
from nil (NULL) object. I believe Rails would attempt to look for both
method and property; however, it would report as undefined
''method'' if
it found nil object.

In your controller, you are using   @story Story.find_by_id(params[:id]) to
search for a story. When a story with
the incoming ID is not found, it returns and assigns nil to your
@story. In your view, you attempt to display ''name'' but it is
being
called from a nil object. If you want to prevent from error, check for
nil (and may take a proper action) before your let Rails render the
action.

Regards,
Taywin

On Jun 17, 6:32 pm, Omar Renteria
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> Well, I''m starting on RoR, so I got a Book called simply
> rails...Following the steps in it sometimes when I try to call a
> property, the browser shows me the next exception:
>
> undefined method `name'' for nil:NilClass
>
> I don''t know why...here''s my controller:
> #Controller starts here
> class StoriesController < ApplicationController
>   before_filter :login_required, :only => [ :new, :create]
>
>   def index
>     get_stories ''votes_count >= 5''
>   end
>
>   def bin
>     get_stories ''''
>     render :action => ''index''
>   end
>
>   protected
>   def get_stories(conditions)
>     @stories = Story.find :all, :order => ''id DESC'',
:conditions =>
> conditions
>   end
>
>   def new
>     @story = Story.new
>   end
>
>   def create
>     #@story = Story.new(params[:story])
>     @story = @current_user.stories.build params[:story]
>     if @story.save
>       flash[:notice] = "La historia a sido agregada
correctamente!"
>       redirect_to stories_path
>     else
>       render :action => ''new''
>     end
>   end
>
>   def show
>     @story = Story.find_by_id(params[:id])
>   end
> end
> #controller ends here
>
> Here''s my view:
> #View starts here
> <h2>
>    <%= @story.name %>
> </h2>
> <h3>
>     <span id="vote_score">
>   Shoveadas => <%= @story.votes.size %>
>     </span>
> </h3>
> <p class="submited_by"> Agregada por: <%=
@story.user.login %> </p>
> <p>
>     <%= link_to @story.link, @story.link%>
> </p>
> <div id="vote_form">
>   <% form_remote_tag :url => story_votes_path(@story) do %>
>     <%= submit_tag ''Shovealo!'' %>
>   <% end %>
> </div>
> <ul id="vote_history">
>   <% if @story.votes.empty? %>
>     <em>Sin shoveadas aun</em>
>   <% else %>
>     <%= render :partial => ''votes/vote'',
:collection => @story.votes %>
>   <% end %>
> </ul>
> #view ends here
>
> From now thank you!
> --
> Posted viahttp://www.ruby-forum.com/.
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But it exists...in deed when I try the same param in rails console the 
object is found.


Taywin wrote:
> If you look at the error "undefined method `name'' for
nil:NilClass,"
> it tells you that the error is from attempting to call a method
''name''
> from nil (NULL) object. I believe Rails would attempt to look for both
> method and property; however, it would report as undefined
''method'' if
> it found nil object.
> 
> In your controller, you are using   @story >
Story.find_by_id(params[:id]) to search for a story. When a story with
> the incoming ID is not found, it returns and assigns nil to your
> @story. In your view, you attempt to display ''name'' but
it is being
> called from a nil object. If you want to prevent from error, check for
> nil (and may take a proper action) before your let Rails render the
> action.
> 
> Regards,
> Taywin
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On 20/06/2010 01:08, Omar Renteria wrote:
> But it exists...in deed when I try the same param in rails console the
> object is found.
<snip>

Are both cases (console and code running on server) running under the 
same environment? E.g. development vs production

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Look at your link_to in the index.html, it should contain the id for
the story you want to show.

Also, check to make sure that you have the to_param method in your
model, story.db and that it''s correct. The author implements a
complicated beautification of the urls which is a waste in the course
of the examples.

I have the same book, one of the best for learning rails imho.

One other question for you - there are some extra methods that are a
bit confusing, your bin method and the get_stories for example. I
don''t think the saving of a few lines of code is worth the possible
confusion.

On Jun 17, 6:32 pm, Omar Renteria
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> Well, I''m starting on RoR, so I got a Book called simply
> rails...Following the steps in it sometimes when I try to call a
> property, the browser shows me the next exception:
>
> undefined method `name'' for nil:NilClass
>
> I don''t know why...here''s my controller:
> #Controller starts here
> class StoriesController < ApplicationController
>   before_filter :login_required, :only => [ :new, :create]
>
>   def index
>     get_stories ''votes_count >= 5''
>   end
>
>   def bin
>     get_stories ''''
>     render :action => ''index''
>   end
>
>   protected
>   def get_stories(conditions)
>     @stories = Story.find :all, :order => ''id DESC'',
:conditions =>
> conditions
>   end
>
>   def new
>     @story = Story.new
>   end
>
>   def create
>     #@story = Story.new(params[:story])
>     @story = @current_user.stories.build params[:story]
>     if @story.save
>       flash[:notice] = "La historia a sido agregada
correctamente!"
>       redirect_to stories_path
>     else
>       render :action => ''new''
>     end
>   end
>
>   def show
>     @story = Story.find_by_id(params[:id])
>   end
> end
> #controller ends here
>
> Here''s my view:
> #View starts here
> <h2>
>    <%= @story.name %>
> </h2>
> <h3>
>     <span id="vote_score">
>   Shoveadas => <%= @story.votes.size %>
>     </span>
> </h3>
> <p class="submited_by"> Agregada por: <%=
@story.user.login %> </p>
> <p>
>     <%= link_to @story.link, @story.link%>
> </p>
> <div id="vote_form">
>   <% form_remote_tag :url => story_votes_path(@story) do %>
>     <%= submit_tag ''Shovealo!'' %>
>   <% end %>
> </div>
> <ul id="vote_history">
>   <% if @story.votes.empty? %>
>     <em>Sin shoveadas aun</em>
>   <% else %>
>     <%= render :partial => ''votes/vote'',
:collection => @story.votes %>
>   <% end %>
> </ul>
> #view ends here
>
> From now thank you!
> --
> Posted viahttp://www.ruby-forum.com/.
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