Self Reference, Almost There (I Hope!)

rubyonrails-talk
1

I'm still struggling with the self reference. I *THINK* I'm getting close. I have the following tables:

class CreateCategories < ActiveRecord::Migration   def self.up     create_table :categories do |t|     t.string :name, :limit => 40       t.timestamps     end   end end

class CreateRelationships < ActiveRecord::Migration   def self.up     create_table :relationships, :id => false do |t|     t.integer :category_id     t.integer :parent_id     t.integer :sort_order       t.timestamps     end   end end

My models look like this:

class Relationship < ActiveRecord::Base   belongs_to :category, :class_name => 'Category',        :foreign_key => 'category_id'   belongs_to :parent, :class_name => 'Category',              :foreign_key => 'parent_id end

class Category < ActiveRecord::Base   has_many :relationships, :foreign_key => 'category_id'

  has_many :parents, :class_name => 'Category',                      :through => 'relationships',                      :source => :parent

  has_many :children, :class_name => 'Category',                       :through => 'relationships',                       :source => :category end

I can create a category. When I try to add a parent to it (e.g. c.parents << p) I get the error

ActiveRecord::HasManyThroughAssociationNotFoundError: Could not find the association "relationships" in model Category

I'm sure that I'm missing something simple, but I don't see it. Can anyone let me know what I'm missing?

Thanks much ---Michael

2

class CreateRelationships < ActiveRecord::Migration def self.up create_table :relationships, :id => false do |t| t.integer :category_id t.integer :parent_id t.integer :sort_order t.timestamps end end end

If "relationships" is a join table, then it can't have any fields other than the two foreign keys.

class Relationship < ActiveRecord::Base belongs_to :category, :class_name => 'Category', :foreign_key => 'category_id' belongs_to :parent, :class_name => 'Category', :foreign_key => 'parent_id end

Right - so Relationship is an AR model - it *needs* an ID column.

There might be some other issues... but get to them after the Relationship models are working (try creating one in the console to make sure it works...)

3

<snip>

Also, you need to refer to the relationships association in the Category class as follows:

has_many :parents, :class_name => 'Category', :through => :relationships, :source => :parent

(In case there's anybody still interested :slight_smile: )