IoC (Ninject) and Factories

Question

If I have the following code:

public class RobotNavigationService : IRobotNavigationService {
  public RobotNavigationService(IRobotFactory robotFactory) {
          


        

Answer 1

I was looking for a way to clean up a massive switch statement that returned a C# class to do some work (code smell here).

I didn't want to explicitly map each interface to its concrete implementation in the ninject module (essentially a mimic of lengthy switch case, but in a diff file) so I setup the module to bind all the interfaces automatically:

public class FactoryModule: NinjectModule
{
    public override void Load()
    {
        Kernel.Bind(x => x.FromThisAssembly()
                            .IncludingNonPublicTypes()
                            .SelectAllClasses()
                            .InNamespaceOf()
                            .BindAllInterfaces()
                            .Configure(b => b.InSingletonScope()));
    }
}

Then create the factory class, implementing the StandardKernal which will Get the specified interfaces and their implementations via a singleton instance using an IKernal:

    public class CarFactoryKernel : StandardKernel, ICarFactoryKernel{
    public static readonly ICarFactoryKernel _instance = new CarFactoryKernel();

    public static ICarFactoryKernel Instance { get => _instance; }

    private CarFactoryKernel()
    {
        var carFactoryModeule = new List { new FactoryModule() };

        Load(carFactoryModeule);
    }

    public ICar GetCarFromFactory(string name)
    {
        var cars = this.GetAll();
        foreach (var car in cars)
        {
            if (car.CarModel == name)
            {
                return car;
            }
        }

        return null;
    }
}

public interface ICarFactoryKernel : IKernel
{
    ICar GetCarFromFactory(string name);
}

Then your StandardKernel implementation can get at any interface by the identifier of you choice on the interface decorating your class.

e.g.:

    public interface ICar
{
    string CarModel { get; }
    string Drive { get; }
    string Reverse { get; }
}

public class Lamborghini : ICar
{
    private string _carmodel;
    public string CarModel { get => _carmodel; }
    public string Drive => "Drive the Lamborghini forward!";
    public string Reverse => "Drive the Lamborghini backward!";

    public Lamborghini()
    {
        _carmodel = "Lamborghini";
    }
}

Usage:

        [Test]
    public void TestDependencyInjection()
    {
        var ferrari = CarFactoryKernel.Instance.GetCarFromFactory("Ferrari");
        Assert.That(ferrari, Is.Not.Null);
        Assert.That(ferrari, Is.Not.Null.And.InstanceOf(typeof(Ferrari)));

        Assert.AreEqual("Drive the Ferrari forward!", ferrari.Drive);
        Assert.AreEqual("Drive the Ferrari backward!", ferrari.Reverse);

        var lambo = CarFactoryKernel.Instance.GetCarFromFactory("Lamborghini");
        Assert.That(lambo, Is.Not.Null);
        Assert.That(lambo, Is.Not.Null.And.InstanceOf(typeof(Lamborghini)));

        Assert.AreEqual("Drive the Lamborghini forward!", lambo.Drive);
        Assert.AreEqual("Drive the Lamborghini backward!", lambo.Reverse);
    }