TinyIoC - Multiple Implementations of Interface

Question

I am just beginning to learn about IoC and Dependency Injection. I am planning on doing a MonoTouch project and wanted to use TinyIoC but I wanted to test it out first. I'm creating a dummy credit card processing console app and I'm having trouble with how to configure TinyIoC since I have multiple implementations of my interface. This is my test app.

Interface:

public interface IPaymentProcessor
{
    void ProcessPayment(string cardNumber);
}

Two Implementations of the interface:

VisaPaymentProcessor

public class VisaPaymentProcessor : IPaymentProcessor
{
    public void ProcessPayment(string cardNumber)
    {
        if (cardNumber.Length != 13 && cardNumber.Length != 16)
        {
            new ArgumentException("Card Number isn't the correct length");
        }

        // some code for processing payment
    }
}

AmexPaymentProcessor

public class AmexPaymentProcessor : IPaymentProcessor
{
    public void ProcessPayment(string cardNumber)
    {
        if (cardNumber.Length != 15)
        {
            new ArgumentException("Card Number isn't the correct length");
        }

        // some code for processing the payment
    }
}

Simple stuff. Now I have a class that accepts the interface as a parameter in the constructor....

CreditCardProcessor

public class CreditCardProcessor
{
    public IPaymentProcessor PaymentProcessor { get; set; }

    public CreditCardProcessor(IPaymentProcessor processor)
    {
        this.PaymentProcessor = processor;
    }

    public void ProcessPayment(string creditCardNumber)
    {
        this.PaymentProcessor.ProcessPayment(creditCardNumber);
    }
}

My console app looks like this....

class Program
{
    static void Main(string[] args)
    {
        TinyIoCContainer.Current.AutoRegister();

        var creditCardProcessor = TinyIoCContainer.Current.Resolve<CreditCardProcessor>();
        creditCardProcessor.ProcessPayment("1234567890123456"); // 16 digits
    }
}

So I am trying to figure out how to tell the Resolve which implementation of the interface to pass to the constructor. If I run this code, I will always use the VisaPaymentProcessor implementation.

So how can I make TinyIoC pass the AmexPaymentProcessor implementation to the constructor rather than the VisaPaymentProcessor(which seems to be the default)?

Answer 1

I haven't used TinyIoC myself, but I suspect you want:

TinyIoCContainer.Current.Register(typeof(IPaymentProcessor),
                                  typeof(AmexPaymentProcessor));

(If you want to use Amex.)

There are various other Register overloads available, including one which takes a name to use, which may be useful when you resolve. It really depends on what you're trying to achieve, which isn't terribly clear from the question.