Database field refuses to be an integer - Rails/Postgres - ruby-on-rails

Question

I am creating a join table, broadly following the Railscast: http://railscasts.com/episodes/17-habtm-checkboxes-revised?view=asciicast
I cannot set the has_many records on the object and get the following error:
2.0.0p353 :012 > invoice.fly_ids
(0.9ms) SELECT "flies".id FROM "flies" INNER JOIN "categorizations" ON "flies"."id" = "categorizations"."fly_id" WHERE "categorizations"."invoice_id" = 1
ActiveRecord::StatementInvalid: PG::Error: ERROR: operator does not exist: integer = character varying
LINE 1: ...ies" INNER JOIN "categorizations" ON "flies"."id" = "categor...
^
HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.
: SELECT "flies".id FROM "flies" INNER JOIN "categorizations" ON "flies"."id" = "categorizations"."fly_id" WHERE "categorizations"."invoice_id" = 1
I can't get it to work and I think it is because the 'categorizations' table is using varchar instead of integer.
My migration file looks like:
class CreateCategorizations < ActiveRecord::Migration
def change
create_table :categorizations do |t|
t.integer :user_id
t.integer :fly_id
t.timestamps
add_index :categorizations, :user_id
add_index :categorizations, :fly_id
end
end
end
However, when I peek at the database table that is created, :user_id and :fly_id are both varchar
Why is it creating these fields as varchar when I am specifying integer in my migration file?
(even if I get this to work, it might not fix the issue...)
Edit:
User Model:
class User < ActiveRecord::Base
....
has_many :invoices
....
end
Invoice Model:
class Invoice < ActiveRecord::Base
attr_accessible :active
validates :user_id, presence: true
belongs_to :user
has_many :categorizations
has_many :flies, through: :categorizations
end
Invoice migration:
class CreateInvoices < ActiveRecord::Migration
def change
create_table :invoices do |t|
t.boolean :active
t.integer :user_id
t.timestamps
end
add_index :invoices, :user_id
end
end
Categorization Model:
class Categorization < ActiveRecord::Base
attr_accessible :fly_id, :user_id
belongs_to :invoice
belongs_to :fly
end
Categorization migration:
class CreateCategorizations < ActiveRecord::Migration
def change
create_table :categorizations do |t|
t.integer :user_id
t.integer :fly_id
t.timestamps
add_index :categorizations, :user_id
add_index :categorizations, :fly_id
end
end
end
Fly Model:
class Fly < ActiveRecord::Base
attr_accessible :description, :name
validates :description, :name, presence: true
has_many :categorizations
has_many :invoices, through: :categorizations
end
Fly migration:
class CreateFlies < ActiveRecord::Migration
def change
create_table :flies do |t|
t.string :name
t.string :description
t.timestamps
end
end
end

Answer 1

HABTM
If you're using HABTM, your tables don't need any primary keys (id):
create_table :invoices_flies, :id => false do |t|
t.references :user
t.references :flies
end
has_many :through
If you're using has_many :through, your table will use a primary key, as it will be a model of its own:
#app/models/user.rb
Class User < ActiveRecord::Base
has_many :categorizations
has_many :flies, through: :categorizations
end
#app/models/fly.rb
Class Fly < ActiveRecord::Base
has_many :categorizations
has_many :users, through: :categorizations
end
#app/models/categorization.rb
Class Categorization < ActiveRecord::Base
belongs_to :fly
belongs_to :user
end
create_table :categorizations do |t|
t.integer :user_id
t.integer :fly_id
end
I think your issue will probably be with the structure of your associations - can you give us some info on how you've set them up?