How do you seed models with HABTM relationships to other seeded models

Question

I'm working on my first Rails(3) App, and looking to seed a bunch of data.

The issue I'm having is that I want to seed some models that have a has_and_belongs_to_many relationship with other models I've just seeded. I'm doing what seems right, but I'm not getting the results I'm expecting.

I have an Asana model (simplified):

class Asana < ActiveRecord::Base
  has_and_belongs_to_many :therapeutic_foci
end

and the TherapeuticFocus model:

class TherapeuticFocus < ActiveRecord::Base
  has_and_belongs_to_many :asanas
end

In my db/seeds.rb, I create some TherapeuticFoci:

tf = TherapeuticFocus.create([
  {:name => 'Anxiety'},
  {:name => 'Asthma'},
  {:name => 'Fatigue'},
  {:name => 'Flat Feet'},
  {:name => 'Headache'},
  {:name => 'High Blood Pressure'},
  {:name => 'Stress'} ])

Then create an Asana:

asanaCreate = Asana.create!([
  { :english_name => 'Mountain Pose', 
    :traditional_name => 'Tadasana', 
    :pronunciation => 'TadaSANA', 
    :deck_set => 'Basic', 
    :type => 'Standing', 
    :therapeutic_foci => TherapeuticFocus.where("name in ('Stress','Flat Feet')")}
])

The result is that the TherapeuticFocus models are created, the Asana is created, but it doesn't create the relationships to the TherapeuticFocus models. The resulting array is empty.

If I run

TherapeuticFocus.where("name in ('Stress','Flat Feet')")

in the rails console, I get the expected two records:

irb(main):010:0> TherapeuticFocus.where("name in ('Stress','Flat Feet')")
=> [#<TherapeuticFocus id: 6, name: "Flat Feet", description: nil, created_at: "2010-10-11     01:48:02", updated_at: "2010-10-11 01:48:02">, 
    #<TherapeuticFocus id: 19, name: "Stress",     description: nil, created_at: "2010-10-11 01:48:02", updated_at: "2010-10-11 01:48:02">]

So, how does one do this?

Or, is there a better way to do this?

Thanks!

POST ANSWER:

I had already added the inflection:

ActiveSupport::Inflector.inflections do |inflect|
    inflect.irregular 'focus', 'foci'
end

My migration for the join tables looks like:

create_table :asanas_therapeutic_foci, :id => false do |t|
  t.references :asana, :therapeutic_focus
end

I'll try changing this to t.belongs_to instead of t.references and see if that works.

Answer 1

Did you register the pluralization for “focus”? It is not defined by default, so you will need to define it (usually in config/initializers/inflections.rb):

ActiveSupport::Inflector.inflections do |inflect|
  inflect.irregular 'focus', 'foci'
end

You also need to make sure your migration has defined the correct join table for the HABTM association. Here is the pertinent part of the “up” migration that I used:

    create_table :asanas do |t|
      t.string :english_name
      t.string :traditional_name
      t.string :pronunciation
      t.string :deck_set
      t.string :type
    end
    create_table :therapeutic_foci do |t|
      t.string :name
    end
    create_table :asanas_therapeutic_foci, :id => false do |t|
      t.belongs_to :asana
      t.belongs_to :therapeutic_focus
    end

I used the models as you quoted.

With those bits in place, I was able to load your seed definitions.