How would you design a system for a Car that has different engine types (Petrol, Diesel, Electric)? Show the OOP model.

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Accepted Answer

I would model Car and Engine using composition rather than creating separate inheritance hierarchies such as PetrolCar, DieselCar, and ElectricCar. The Car depends on an IEngine abstraction, and concrete engines implement the behavior. This follows programming to an interface and makes adding another engine type possible without modifying Car. public interface IEngine
{
 void Start();
 void Stop();
}

public class PetrolEngine : IEngine
{
 public void Start() => Console.WriteLine("Petrol engine started");
 public void Stop() => Console.WriteLine("Petrol engine stopped");
}

public class ElectricEngine : IEngine
{
 public void Start() => Console.WriteLine("Electric motor started");
 public void Stop() => Console.WriteLine("Electric motor stopped");
}

public class Car
{
 private readonly IEngine engine;

public Car(IEngine engine)
 {
 this.engine = engine;
 }

public void Start() => engine.Start();
 public void Stop() => engine.Stop();
} Car has an Engine rather than inheriting from an engine. The engine abstraction isolates Car from concrete engine implementations. New engines can be introduced without modifying Car. Dependency injection can select the engine at runtime or configuration time. This design supports Open/Closed Principle and composition over inheritance.

How would you design a system for a Car that has different engine types (Petrol, Diesel, Electric)? Show the OOP model.

Car and Engine Using Composition

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