similar to: Model.Save causing nil object error

Dear Rubyists/Rails gurus, Though I''ve successfully completed the various Rails tutorials online and the Depot application from the Agile Web Development with Rails book, I''m still pretty much a Ruby/Rails newbie. I''m trying to learn by writing my own simple blogging application, but I''ve run into a problem that has had me scratching my head for a few days now.

With ref to my previous post: http://www.ruby-forum.com/topic/180356 I am now able to access items from topics controller. However, now I need to add sub-item e.g.: An item itself could have many sub-items. So my items model is like: class Item < ActiveRecord::Base validates_uniqueness_of :title, :scope => [:topic_id] validates_presence_of :topic_id, :title, :owner, :position

I have been trying to model a labeled graph using ActiveRecord (trunk version). Basically, I have a ''Node'' model which represents a node linking to other nodes. Links (aka edges) are labeled (i.e., have a ''label'' attribute and other behavior). Thus I decided to model edges as an ''Edge'' model and use a ''has_many :trough''

on previous apps i hadn''t really worried much about adding foreign key indexes on my tables just because they''ve been fairly small and i didn''t really think i needed them. well, i''m working on something now that has the potential to have a lot more data, and a lot more foreign keys. so i have 3 tables... users, projects, and tasks.. should i be using add_index

Hello, Say, I have a pictures table, and there are many objects which can have pictures, so I define a picturable type. Now, to make the query for pictures more efficient I should index the picture table using both picturable_type and picturable_id. Is this the correct approach to indexing the table, or can things be done better? I want the database retrieval operation to be extremely fast (I

If I ''find'' using :include, and some included associations are null, then looping through the array executing ''if obj[i].assoc'' accesses the database for a second time (as obj.assoc is nil). eg Topic, has_many posts Post has_one email and posts = Post.find(:all, :condition => ''posts.topic_id = 10'', :include =>

Hello guys, I''m a newbie in RoR and I have a problem. My DB structure is ====================================== topics table : id(int,11) name(varchar,255) categories : id (int,11) topic_id(varchar,255) name(varchar,255) ====================================== --Models:-- class Topic < ActiveRecord::Base has_many :categories end class

Hi I''m new to Rails. This is my first application and I''m trying to set up a schema I''ve hand-crafted as a migration. Does anybody know why this... # deposit_types create_table :deposit_types do |table| table.column :type_code, :string, :limit => 20, :null => false table.column :description, :string, :limit => 50, :null => false

The upgrade to Rails 1.1 hurt my ability to run tests because it generated the following MySQL error: Mysql::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''key ON config (key)'' at line 1: CREATE UNIQUE INDEX key ON config (key) I have a table called `config` with a column

I have a User and Topic model. A user subscribes to a topic, so there is a many-to-many relationship between User and Topic. So my User model object is using has_many_and_belongs_to :topics and vice versa. I want to find all the topics that a user has *not* subscribed to. This is what I''ve got: @user = User.find(params[:id]) @topics = Topic.find(:all, :conditions =>

I''m trying to use collection_select, but it''s not working as I expect. The list populates correctly but the current value is not selected. @question contains a topic (via topic_id), and @topics is the list of all topics. Here''s my attempt to create a drop-down list of the topics. form("question") do | form | form << content_tag("b",

After creating a table in a create table migration, I''m then attempting to populate a couple of rows of data in the table using the create method. The first row gets inserted into the database, but any further calls generate a select against the database, but no insert. Am I doing something wrong, or is it inappropriate to create more than a single row of data in a table using

The AWDwR book has the following: add_index :categories_products, [:product_id, :category_id] add_index :categories_products, :category_id The first, composite index actually serves two purposes: it creates an index which can be searched on both foreign key columns, and with most databases it also creates an index that enables fast lookup by the product id. The second index then completes

Hello, We''re using Rails on an Oracle database. If we define an index like the following, we end up with problems during the "db:schema:dump" rake target. add_index "emcolumn", ["upper(name)"], :name => "ind_emcolumn_uname" The created schema.rb file contains: add_index "emcolumn", ["sys_nc00013$"], :name =>

The error occurred while evaluating nil.prefetch_primary_key? Hi, I have a problem with a model when I have 3 belongs_to relations in one the middle. This example is a subset of a grid-routing project: n 1 1 n +------------ Project Connection ------- ConnectionCost +------------ WaySearchRun

Is it possible to put conditions relative to the current instance in has_many''s :conditions? For example, in a forum app: class Post < ActiveRecord::Base belongs_to :topic has_many :self_and_descendants, :class_name => "Post", :order => "lft", :conditions => "topic_id = #{topic_id} AND (lft BETWEEN #{lft} AND #{rgt})" end With the

Hey Folks, I can''t really glean this from the documentation. Is there a way to do: add_index(table_name, column_name, index_type) within my migration for an index that spans multiple columns? Ie: A covering index on FIRST_NAME, LAST_NAME or something like that? Best, Brian --------------------------- Brian Corrigan ---------------------------

So I have the following model class Topic < ActiveRecord::Base belongs_to :topic has_many :topics, :order => :position acts_as_tree :order => :position acts_as_list :scope => :topic_id end that I use for a site''s navigation. Everything (list, create, edit, even the drag&drop sort) works fine, except the destroy function, which the vanilla version def destroy

in lib/active_record/connection_adapters/abstract/schema_statements.rb there is a missing quote_table_name in line 286 (def remove_index): execute "DROP INDEX #{quote_column_name(index_name(table_name, options))} ON #{table_name}" so my "keys" table can get an index with "add_index" but can''t remove it (without tweaking) replacing it to execute

Hi list, I made an open source CMS powered by Rails, named Rubricks. I have a web page for Rubricks. You can download it or view a flash demo there. Please try them and feed me back, like bug report etc. Check it out at: http://rubricks.org/index_en.html Thanks. Shouta