When to Use Ruby Inheritance Versus Mixins

In Ruby, I prefer to use inheritance to establish a subtype from an existing object; to say for example that a Car is a kind of Vehicle.

But to use mixins as a way to reuse code. Car and Aircraf, for example, are both kind of vehicles but a Car may include a Wheeled mechanism while an Aircraft an Air::Skied one:

Car and Aircraf both vehicles but Car includes a Wheeled mechanism while Aircraft an Air::Skied
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class Vehicle; end

class Car < Vehicle
  include TransportationMechanism::Land::Wheeled
end

class Aircraft < Vehicle
  include TransportationMechanism::Air::Skied
end

Decisions regarding what is what deeply depends on your domain knowledge so you’ll end up with a subjective solution hopefully producing a code nice to read then easy to understand.

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