如何列出属于另一个模型的所有模型？

Question

I'm building a small system for a restaurant.

I'm currently stuck at listing efficiently all the models that belong to a product_type the types are: food , beverages , and apparel_items .

Each product Type has multiple kinds of products that belong to them for example food has many wraps , many salads , many sandwiches , etc.

The point of this is to have a button for each of the Product Types which when clicked, depending on the id of the type selected, lists all the models that belong to it as buttons so in turn you can click any of them and then list the database records for the model in question.

Example: Food, Beverages => click food => shows buttons for: wraps, salads and sandwiches => click wraps => Lists all the wraps

class ProductType < ActiveRecord::Base
  has_many :apparel_items
  has_many :chapata_items
  has_many :combos
  has_many :croissants
  has_many :fruits
  has_many :green_challenges
  has_many :hot_drinks
  has_many :infusions
  has_many :juices
  has_many :molletes
  has_many :omelettes
  has_many :salads
  has_many :sandwiches
  has_many :shakes
  has_many :sincronizadas
  has_many :slices
  has_many :smooth_drinks
  has_many :super_drinks
  has_many :water_drinks
  has_many :wrap_items
end

How can I list all the models that belong to another one so that I can program this efficiently?

Would it be better to create a model for each of the Product Types (Food, Beverages, Apparel Items) and make only those three belong to the Product Type model?

Answer 1

You can use ActiveRecord::Reflection to inspect the associations for any model.

So Food.reflect_on_all_associations(:has_many) returns an array of ActiveRecord::Reflection::HasManyReflection objects, with one for each food type that your Food model has_many of. Each of these reflections has a name, which is the name you set when you declare the has_many relationship.

You can then use the names of these reflections to build the list of products like so:

food_product_types = Food.reflect_on_all_associations(:has_many).map(&:name)

# 'food_product_types' equals [:wraps, :salads, :sandwiches, etc...]
# Now, create buttons for each food product type

Of course, if your product types have associations that are not products, you will need to filter them out.

Answer 2

Your schema could certainly benefit from some denormalizing. There are many ways to approach the design, including suggested by you separation of models for product groups.

But, more importantly, you should consider why are you trying to put all the various products into separate models. Are they really that different from the standpoint of the workflow that uses them?

Maybe it worth it to just keep the truly shared set of fields in the Product model and put all the additional attributes into Attribute model? The product_type then will become just a field of Product and you will be able to do lots of wonderful stuff in a straightforward and performant manner.