Question

I have a validation interface like so:

public interface IValidation<T> {
  bool IsValid(T item, ref AggregateException fail);
}

I have a file importer that needs several validation interfaces

public FileImporter {
  IEnumerable<IValidation<Patient>> Validators { get; set; }

  public FileImporter(IWindsorContainer container) {
    // the ResolveAll method does not do this
    Validators = container.ResolveAll<IValidation<Patient>>("fileValidation");
  }
}

I also have another class that has more validators but uses some of the same ones used in FileImporter.

public PatientService {
  IEnumerable<IValidation<Patient>> Validators { get; set; }

  public PatientService(IWindsorContainer container) {
    // the ResolveAll method does not do this
    Validators = container.ResolveAll<IValidation<Patient>>("userInputValidation");
  }
}

For example I have two validators LastNameValidator and DateOfBirthValidator. LastNameValidator is used in both theFileImporterand thePatientService.DateOfBirthValidatoris only used in thePatientService` class. The implementation of these two classes are below the question.

My question is how can i wire up these two classes so that they are used as described above. And what method call should I make to resolve them?

public class LastNameValidator : IValidation<Patient> {
  public bool IsValid(Patient p, ref AggregateException fail) {
    var isValid = !string.IsNullOrWhitespace(p.LastName))
    if (!isValid)
        // update fail
    return isValid;
  }
}

public class DateOfBirthValidator : IValidation<Patient> {
  public bool IsValid(Patient p, ref AggregateException fail) {

    if (!p.DateOfBirth.HasValue) {
        // update fail, can't be empty
        return false;
    }
    if (p.DateOfBirth.Value > DateTime.Now) {
        // update fail, can't be in future
        return false;
    }
    return true;
  }
}

Answer 1

I would consider the Typed Factory Facility. You could register your validators with the names “lastnamevalidator” and “dobvalidator”. Then create a factory interface for grabbing those specific validators. You just need the interface — the facility will do the implementation:

public interface IValidatorFactory
{
    IValidator GetLastNameValidator();
    IValidator GetDobValidator();
}

Now pass the IValidatorFactory to your component. This also removes the need to pass the Windsor container around (which isn’t a good idea as it tightly couples your code to Windsor and makes unit testing more difficult).

Now just call the factory methods to access the particular validator each component needs.

UPDATE:

Still not clear on which part of your system is going to determine which IValidators to use, but maybe this would work. Use a marker inteface that is based on IValidator.

public interface IFileValidator : IValidator
{
}

public interface IUserInputValidator : IValidator
{
}

Now have your validators implement the marker interfaces depending on where they are going to be used — and remember you can implement multiple interfaces so validators can be used in multiple situations. Example:

public class FileValidator : IFileValidator
{
    public bool IsValid()
    {
        return false;
    }
}

public class DobValidator : IUserInputValidator, IFileValidator
{
    public bool IsValid()
    {
        return false;
    }
}

public class LastNameValidator : IUserInputValidator
{
    public bool IsValid()
    {
        return true;
    }
}

Change the factory interface to return just the specific types of validators:

public interface IValidatorFactory
{
    IFileValidator[] GetFileValidators();
    IUserInputValidator[] GetUserInputValidators();
}

Now register the validators accorindg to their “type”. If a validator has multiple uses, make sure to add a .Forward<> defintion for Windsor:

var container = new WindsorContainer();
container.AddFacility<TypedFactoryFacility>();
container.Register(
    Component.For<IValidatorFactory>().AsFactory(),

    Component.For<IFileValidator>().ImplementedBy<FileValidator>(),
    Component.For<IUserInputValidator>().ImplementedBy<LastNameValidator>(),
    Component.For<IFileValidator>().Forward<IUserInputValidator>().ImplementedBy<DobValidator>()
    );