How to get list of categories for a store

I have a Store Model that can have multiple products. Each product has a category.

What is the most optimal way to g开发者_JAVA百科et the list of categories for products in a store?

For eg. Store A has Products A (Cat1), Product B(Cat1), Product C (Cat2)

I want Cat1, Cat2 when I pass the Store A's id.

@store = Store.find(ID)
@categories = @store.products.map {|p| p.category }

So,

1. Store has_many products (each product belongs_to Store): one-to-many relation
2. Each product has_one category (each category belongs_to a product): one-to-one relation

In your Product table, you should have store_id field, and in your Category table you should have a product_id field. Then set the has_many and belong_to relation in your Models.

# beware of the use of pluralization

# Store model
class Store < ActiveRecord::Base
  has_many :products                    
end

# Product model
class Product < ActiveRecord::Base
  belongs_to :store
  has_one :category
end

# Category model
class Category < ActiveRecord::Base
  belongs_to :product
end

# e.g. access category of a product in your Store Controller
# or loop it in your Store view
@store = Store.find_by_id(myInt)
@firstProductCategory = @store.products[0].category.name