Ruby on Rails

i=Item.first

i.item_properties

NameError: uninitialized constant Item::ItemProperties

class Item < ApplicationRecord
 has_many :boxes
 has_many :item_pictures
 has_many :pictures, through: :item_pictures
 has_many :item_item_properties, primary_key: 'item_type', foreign_key: 'item_type'
 has_many :item_properties, through: :item_item_properties
 ITEM_TYPES =  ['General', 'Book', 'Record', 'Magazine', 'Pez dispenser', 'CD', 'VHS casette']
 validates :item_type, inclusion: ITEM_TYPES
 attr_accessor "Year"
 
end

class ItemItemProperty < ApplicationRecord
 belongs_to :items, primary_key: 'item_type', foreign_key: 'item_type'
 belongs_to :item_properties, primary_key: 'item_type', foreign_key: 'item_type'
end