Question

Not able to understand why the same command Category.find(:all , :order => 'name ASC') works in the rails console but not returning anything in the template and controller
please help

_form.html.erb

<% @all_categories.each do |cat| -%>
  <li><%= check_box_tag('categories[]' , cat.id , @post.categories.collect{|c| c.id}.include?(cat.id))%>
  <%= cat.name %></li>
<% end -%>

posts_controller.rb

@all_categories = Category.find(:all , :order => 'name ASC')  

rails console

@all_categories = Category.find(:all , :order => 'name ASC')
  Category Load (0.2ms)  SELECT `categories`.* FROM `categories` ORDER BY name ASC
 => [#<Category id: 1, name: "General", short_name: "general", description: "This is a general category">] 

error

undefined method `each' for nil:NilClass

posts_controller

  def edit
    @user_list = get_user_list
    @post = Post.find(params[:id])
  end
  def update
    post_params = params[:post]
    author_id  = post_params.delete(:author_id)
    #@all_categories = get_all_categories
    @all_categories = Category.find(:all , :order => 'name ASC')  
    checked_categories = get_categories_from(params[:categories])
    removed_categories = @all_categories - checked_categories
    @post = Post.find(params[:id])
    @post.author = User.find(author_id) if @post.author_id != author_id 
    if @post.update_attributes(post_params)
      perform_operation_on_categories
      flash[:notice] = "Post was successfully updated."
      redirect_to :action => 'show' , :id => @post
    else
      @user_list = get_user_list
      render :action => 'edit'
    end

  end

index view

<h1><% @page_title = 'Listing posts' %></h1>
<%= content_tag('p',link_to('&laquo Back', :controller => 'staff',:action =>'menu')) %>
<table>

    <tr>
        <th>Created at</th>
        <th>Title</th>
        <th>Author</th>
        <th>Categories</th>
        <th>Status</th>
        <th>Comments</th>
    </tr>

<% @posts.each do |post|    %>
<tr class="<%= cycle('row1','row2') %>">
    <td><%= post.created_at.strftime('%m/%d/%y %I:%m %p')%></td>
    <td><%= h(post.title)%></td>
    <td><%= h(post.author.display_name) if post.author%></td>
    <td><%= post.categories.collect {|cat| cat.name}.join(", ")%></td>
    <td><%= h(post.status)%></td>
    <td><%= post.comments_count %></td>
    <td><%= link_to('Preview',{:action =>'show',:id=>post,:target => '_blank'})%></td>

    <td><%= link_to 'Edit', edit_post_path(post) %></td>
    <td><%= link_to 'Delete', post, :method => :delete, :data => { :confirm => 'Are you sure you want to permanently remove this post?' } %></td>
</tr>
<% end %>
</table>

<%= will_paginate(@posts) %>
<br/>
<%= link_to 'New Post' , :action=> 'new' %>

_form.html.erb (the part where i am getting error)

<table>
    <tr>
        <th>Title</th>
        <td><%= text_field(:post,:title,:size => 40 , :style => "font-size: 1.5em;")%></td>
        <td rowspan="2">
            <div class="categorylist">
                <h2>Categories:</h2>
                <ul>

                        <% @all_categories.each do |cat| -%>
                            <li><%= check_box_tag('categories[]' , cat.id , @post.categories.collect{|c| c.id}.include?(cat.id))%>
                            <%= cat.name %></li>
                        <% end -%>

                </ul>

edit.html.erb

<% @page_title = 'Edit Post' -%>

<%= content_tag('p',link_to('&laquo; Back', :action => 'index'))%>

<%= form_tag(:action => 'update') do -%>
    <%= render(:partial => 'form')%>
    <%= submit_tag('Create', :style => 'margin: 1.5em 0 0 100px;')%>

<% end %>

<%= link_to('Preview Post' , {:action=>'show',:id => @post} ,:target => '_blank')%>

Answer 1

Just guessing from the code you posted but it seems to me that you should put the


@all_categories = Category.find(:all , :order => 'name ASC')


in the edit method that will be called to display your view and not only in the update method that will be called to persist your changes.

The same eventually applies to new, index and show methods

HTH