Question

I have a tutorials model that looks like this:

class Tutorial < ActiveRecord::Base
  attr_accessible :content, :title
  has_many :tutorial_categories
end

and a tutorial_category model that looks like this:

class TutorialCategory < ActiveRecord::Base
  attr_accessible :name, :tutorial_id
  belongs_to :tutorial
end

When I know the tutorial_category via something like @tutorial_category = TutorialCategory.find(params[:id])

How can I get all the tutorials that belong to that tutorial category. Put another way, once I know @tutorial_category.name, I want all tutorials that have the same tutorial_category.name set.

Do I need to use a join or include to do this?

Answer 1

First you’re using the wrong type of relationship here. You’re trying to model a many to many relationship with a many to one setup. I’d setup your models like the following. This assumes you have a join table called categories_tutorials with the fields category_id and tutorial_id. Also note I changed the name of your categories model as it was very close to the conventional Rails join table syntax.

class Tutorial < ActiveRecord::Base
  attr_accessible :content, :title
  has_and_belongs_to_many :categories
end

class Category < ActiveRecord::Base
  attr_accessible :name
  has_and_belongs_to_many :tutorials
end

To find all the Tutorials for a given category you can now do something like the following:

a = Category.find(:params[:id])
tutorials = a.tutorials