Factory class is not supporting SOLID principle

Question

I have code as shown below

 public interface ICar
{
    void Created();
}

public class BigCar : ICar
{
    public void Created()
    {

    }
}

public class SmallCar : ICar
{
    public void Created()
    {

    }
}


public class LuxaryCar : ICar
{
    public void Created()
    {

    }
}

public class CarFactory
{
    public ICar CreateCar(int carType)
    {
        switch (carType)
        {
            case 0:
                return new BigCar();
            case 1:
                return new SmallCar();
            case 2:
                return new LuxaryCar();
            default:
                break;
        }
        return null;
    }
}

In this code I have a factory which is returning the concrete instances. But every time I need to have a new implementation of the ICar interface, I have to change the CreateCar() method of the CarFactory. It seems like I am not supporting the Open Closed Principle of the SOLID principles. Please suggest is there a better way to handle this scenario.

Answer 1

You probably want to make it configurable, like this:

void Main()
{
    // configurable array
    var factories = new ICarFactory[] { new BigCarFactory() };

    // create factory
    var realfactory = new CarFactory(factories);

    // create car
    var car = realfactory.CreateCar(0);
}

public class CarFactory : ICarFactory
{
    private ICarFactory[] _factories;

    public CarFactory (ICarFactory[] factories)
    {
        _factories = factories;

    }   
    public ICar CreateCar(int carType)
    {
        return _factories.Where(x=>x.SupportCar(carType)).First().CreateCar(carType);
    }

    public bool SupportCar(int type) => _factories.Any(x=>x.SupportCar(type));
}

public interface ICarFactory
{
    ICar CreateCar(int type);
    bool SupportCar(int type);
}

public class BigCarFactory : ICarFactory
{
    public ICar CreateCar(int carType)
    {
        if(carType != 0) throw new NotSupportedException();
        return new BigCar();
    }

    public bool SupportCar(int type) => type == 0;
}


public interface ICar
{
    void Created();
}

public class BigCar : ICar
{
    public void Created()
    {

    }
}

public class SmallCar : ICar
{
    public void Created()
    {

    }
}


public class LuxaryCar : ICar
{
    public void Created()
    {

    }
}