Let's prepare different types of insurance as follows:
# app/models/pilot.rb class Pilot < AeroSpace embeds_many :insurances, as: :insurable end # app/models/car_driver.rb class CarDriver < Terrestrial embeds_many :insurance, as: :insurable end # app/models/astronaut.rb class Astronaut < AeroSpace embeds_many :insurances, as: :insurable end
And now we design the Insurance class as follows:
# app/models/insurance.rb class Insurance include Mongoid::Document embedded_in :insurable, polymorphic: true end # app/models/travel_insurance.rb class TravelInsurance < Insurance end # app/models/theft_insurance.rb class TheftInsurance < Insurance end
Now let's provide insurance policies for our drivers as follows:
irb> p = Pilot.first
=> #<Pilot _id: 4ef9a410fed0eb977d000002, _type: "Pilot", name: "Gautam", age: nil, address: {"street"=>"asfds", "city"=>"Pune", "_id"=>BSON::ObjectId('4f0491bcfed0ebcc59000001')}, weight: nil, gforce: nil>
irb> p.insurances << TravelInsurance.new
=> [#<TravelInsurance _id: 4f06ad2efed0ebe598000002, _type: "TravelInsurance">]
irb> a = Astronaut.first
=> #<Astronaut _id: 4f069fd8fed0ebe45d000001, _type: "Astronaut", name: nil, age: nil, address: nil, weight: nil, gforce: nil>
irb> a.insurances << TravelInsurance.new
=> [#<TravelInsurance _id: 4f06b058fed0ebe598000004, _type: "TravelInsurance">]
irb> a.insurances << FireInsurance.new
=> [#<FireInsurance _id: 4f06ad6bfed0ebe598000003, _type: "FireInsurance">]
irb> a.insurances
=> [#<FireInsurance _id: 4f06ad6bfed0ebe598000003, _type: "FireInsurance">, #<TravelInsurance _id: 4f06b058fed0ebe598000004, _type: "TravelInsurance">]
Let's have a closer look at the preceding commands:
irb> p = Pilot.first
=> #<Pilot _id: 4ef9a410fed0eb977d000002, _type: "Pilot", name: "Gautam", age: nil, address: {"street"=>"asfds", "city"=>"Pune", "_id"=>BSON::ObjectId('4f0491bcfed0ebcc59000001')}, weight: nil, gforce: nil>
irb> p.insurances << TravelInsurance.new
=> [#<TravelInsurance _id: 4f06ad2efed0ebe598000002, _type: "TravelInsurance">]
Here, Insurance is polymorphic. This means that the Insurance object can be embedded in multiple parents. In this case, we have TravelInsurance (that is, a model, which inherits from Insurance) being assigned to the Pilot class:
irb> a = Astronaut.first
=> #<Astronaut _id: 4f069fd8fed0ebe45d000001, _type: "Astronaut", name: nil, age: nil, address: nil, weight: nil, gforce: nil>
irb> a.insurances << TravelInsurance.new
=> [#<TravelInsurance _id: 4f06b058fed0ebe598000004, _type: "TravelInsurance">]
Now, we have the TravelInsurance object being embedded in the Astronaut class. This shows us the polymorphic nature of the Insurance embedded object — it can be embedded in different parents.
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