Polymorphic relations

Polymorphic means multiple forms or multiple behaviors. For example, a vehicle could mean a two-wheeler, three-wheeler, a car, a truck, or even a space shuttle! So, how do we map these different types of vehicles that have entirely different data but have a relatively common functionality? Enter polymorphic relations! Let's create vehicles using basic polymorphism.

Let's design the Vehicle model:

# app/models/vehicle.rb

class Vehicle
  include Mongoid::Document

  belongs_to :resource, polymorphic: true

  field :terrain, type: String
  field :cost, type: Float
  field :weight, type: Float
  field :max_speed, type: Float
end

This is the main polymorphic class. We now use this class in other models. Now, each model we build is independent and can choose to be related to Vehicle. It has its own identity and does not inherit from any parent model, but it will be treated like a vehicle.

Let's create a Bike class:

# app/models/bike.rb
class Bike
  include Mongoid::Document
...