CODEWITHSUNDEEP
ruby-on-railsassociations
tehfailsafe
tehfailsafe

Reputation: 3451

rails find similar products other customers ordered

I have a simple app where users can view products and preorder them so they have one in stock when they get released.

A Product has many preorders, and many users through preorders.

A User has many preorders, and many products through preorders.

I would like to show other products that other people have preordered to when you view a product. I've tried many combinations of joins where etc, but I'm not sure how to wrap my head around it.

When viewing a product I need to find all the users who have preordered this specific product. Then I need to list all of the products those users have preorders for, and ideally they would be ordered by the number of times they have been preordered.

Upvotes: 0

Views: 308

Answers (1)

sites
sites

Reputation: 21803

I am not sure if this is the answer you are looking for, but I'll try.

product.users # Gives you the users with preorders for that specific product.

For all products those users have preordered: 

user.preorders # will give you all preorders for a given user.

Update

You have a product, you want to get more products according users who have preordered product, to make a list of tuples (product, preorders_count).

products = product.users.products # products not defined yet, see below

User model

def self.products
  # [[pid1, pid2], [pid1], [pid2]]
  # includes to reduce the number of queries
  product_ids = includes(:products).all.map(&:product_ids)
  # [pid1, pid2]
  product_ids.flatten!.uniq!
  # return a relation ,so you can call product.users.products.where...
  Product.where id: product_ids
end

Then you can use:

products.each do |product|
  product.preorders.size
end

Suggestion

You can use a cached counter for preorders in products table

rails g migration add_preorders_count_to_products preorders_count:integer
# verify your migration
rake db:migrate

and in preorder model:

belongs_to :product, counter_cache: true

I have not tested this all, can you?

Upvotes: 1

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