Problems with nil object

Rails
1

Hi to all. I’ve a very big problem. I know this can seem very loing, but
please, try to read it. I have a simply blog, with posts and their
comments. I’ve two tables in my db, posts, with post id, text and
comments_count to store the number of comments-children of each post (as
recomanded to do in AWDWR); and the table comments, with comment id,
post_id for the post they’re referred to, and text (there are many other
fields, but they’re not importat here). I have a home_controller, this
is the code:

class HomeController < ApplicationController

def index
  @posts = Post.find(:all, :order => "data DESC")
end

def show_comment
  @posts = Post.find(:all, :order => "data DESC")
  @comments = Comment.find(:all, :conditions => ['post_id= ?',

params[:id] ])
end

def add_comment
  @posts = Post.find(:all, :order => "data DESC")
  @comments = Comment.find(:all, :conditions => ['post_id= ?',

params[:id] ])
@com = Comment.new(:post_id => params[:post_id])
if flash[:comment]
@comment = flash[:comment]
else
@comment = Comment.new
end
end

def save_comment
  if request.post?
    @comment = Comment.new(params[:comment])
    if @comment.save
      flash[:notice] = "Commento inserito con successo"
      redirect_to("/home/show_comment/" +

params[:comment][:post_id])
else
flash[:comment] = @comment
redirect_to("/home/add_comment/" + params[:comment][:post_id])
end
end
end

end

and three views, index, add_comment and show_comment.

The problem arise with add_comment. When i want to add a comment for a
post without any comment (i’m the first to insert a comment for a post),
it displays:

You have a nil object when you didn’t expect it!
The error occurred while evaluating nil.post_id

Extracted source (around line #17):

14:


15: <% end %>
16: <% end %>
17: <%= com.post_id %>
18: <% if @com.post_id == post.id %>
19: <%= error_messages_for :comment %>
20: <% form_for @comment, :url => {:action => :save_comment} do |form| %>

This is the code for the add_comment page

 <% for post in @posts %>
  <div class="post">
      <p>Titolo: <%= post.titolo %> <span>data: <%= post.data

%>


Testo:
<%= post.testo %>


<%= link_to ‘Commenti(’ + post.comments.size.to_s + ‘)’,
:action => ‘show_comment’, :id => post %>
<%= link_to ‘Aggiungi un commento’, :action =>
‘add_comment’, :id => post %>

<% for com in @comments %>
<% if com.post_id == post.id %>


<%= com.testo %>


<% end %>
<% end %>
<% if com.post_id == post.id %>
<%= error_messages_for :comment %>
<% form_for @comment, :url => {:action =>
:save_comment} do |form| %>


Autore:

<%= form.text_field :autore%>



Testo:
<%= form.text_area :testo %>


<%= form.hidden_field :post_id, :value =>
post.id %>
<%= submit_tag “Invia commento” , :class =>
“submit” %>
<% end %>
<%end%>
  </div> <!-- post -->
  <% end %>

PLEASE HELP ME to solve this problem!

2

On 14 Apr 2008, at 12:20, Emanuele B. wrote:

fields, but they’re not importat here). I have a home_controller, this
<% if com.post_id == post.id %>
com isn’t defined here. What are you expecting it to be

Fred

3

Line 16 closes the “for com in @comments” loop so “com” goes out of
scope. That’s why you are getting the nil error. I think you want to
move that <% end %> further down. Think through what the loop should
be doing and make sure it wraps all that code.

:slight_smile:

-Danimal