Association through another table "Unknown key: through"(Rails)

associations, has-many-through, ruby-on-rails

Solution

class Category < ActiveRecord::Base
  attr_accessible :name
  has_many :tripcategories
  has_many :trips, :through => :tripcategories
end

Problem

I'm creating trips in my rails app and i want to add categories to those trips. The categories are stored in the Categories table in my DB and the user may select which categories are suitable for the trip. So multiple categories a trip can be used. Although i'm a noob i figured some things out with some help of the RoR guides about this subject. Now, i've got a 3rd table tripcategories which will have to hold the trip_id and the category_id. Right? With that i've got the following models: trip.rb: ``` class Trip < ActiveRecord::Base attr_accessible :description, :title, :user_id, :triplocations_attributes, :photo has_many :triplocations, :dependent => :destroy has_many :tripcategories has_many :categories, :through => :tripcategories accepts_nested_attributes_for :triplocations, allow_destroy: true end ``` category.rb: ``` class Category < ActiveRecord::Base attr_accessible :name has_many :tripcategories belongs_to :trip, :through => :tripcategories end ``` tripcategory.rb: ``` class Tripcategory < ActiveRecord::Base attr_accessible :category_id, :trip_id belongs_to :trip belongs_to :category end ``` When i'm trying it this way and trying to call trip.categories in my trip index it says `"Unknown key: through"`. Am i doing something horribly wrong or am i missing the bigger picture? Thanks in advance!

Original source