Question

So I’ve got three models:

• User
• User Interest
• Interest Tags

User Model

class User < ActiveRecord::Base
  has_many :user_interests 
end

InterestTag Model

class InterestTag < ActiveRecord::Base
 has_many :user_interests, :dependent => :destroy

validates :name, :uniqueness => true

end

UserInterest Model

class UserInterest < ActiveRecord::Base
  belongs_to :interest_tag
  belongs_to :user
end

I’d like to use ActiveRecord to include the name of the user’s interests when loading their profile using the following query:

@user = User.find(current_user.id, :include => [{:user_interests => :interest_tags}])

Migrations for interest_tags + user_interests

create_table :interest_tags do |t|
  t.string :name, :null => false, :size => 30
  t.timestamp :created_at
end

create_table :user_interests do |t|
  t.integer :user_id
  t.integer :interest_tag_id
end

What am I doing wrong?

Answer 1

You have to add an has_many :through association on User model.

class User < ActiveRecord::Base
  has_many :user_interests 
  has_many :interest_tags, :through => :user_interests
end

class UserInterest < ActiveRecord::Base
  belongs_to :interest_tag
  belongs_to :user
end

class InterestTag < ActiveRecord::Base
  has_many :user_interests, :dependent => :destroy
  validates :name, :uniqueness => true
end

Now you can eager load the tags as follows:

User.find(current_user.id, :include => :interest_tags)

Note:

You might want to look at the acts_as_taggable_on gem for your requirement.