2008-02-09

Validation

I have a model like so

Product 1----* ProductVersion
ProductVersion 1----* ProductEdition

ProductVersion can been in one of two states: UnderDevelopment / Released

ProductEdition has a DownloadUrl:string attribute which is only required if self.version.status = #Released


The validation for ProductEdition works perfectly, I cannot leave the DownloadUrl blank if the ProductVersion has already been released. Unfortunately when I already have a number of ProductEdition

instances with no DownloadUrl and then make my Productversion live the editions are not validated because they are not dirty. So I needed some way to ensure that when ProductVersion is validated all related

ProductEdition instances are also validated.

Step 01: Add a way to allow ProductVersion to identify other objects to be validated.

In the business classes project I added the following interface.

public interface IValidationExtender
{
  IEnumerable GetConstraintedObjects();
}


My ProductVersion can do this

IEnumerable IValidationExtender.GetConstraintedObjects()
{
  List result = new List();
  foreach (IObject currentEdition in Editions)
    result.Add(currentEdition.AsIObject());
  return result;
}



Step 02: Create a validation service which validates all objects : Only implemented methods are shown

public class ExtendedConstraintProvider : IConstraintProvider
{
 private IConstraintProvider ModeledConstraintProvider;

 public void GetConstraintsForObject(IObject instance, List constraints)
 {
    if (instance == null)
      throw new ArgumentNullException("instance");

    //Deletegate to GetConstraintsForObjects
    GetConstraintsForObjects((IObjectList)instance.GetAsCollection(), constraints);
  }

  public void GetConstraintsForObjects(IObjectList objectList, List constraints)
  {
    if (objectList == null)
      throw new ArgumentNullException("objectList");
    if (objectList.Count == 0)
      return;

    //Get all constrained objects
    Dictionary includedObjects = new Dictionary();
    foreach (IObject currentObject in objectList)
      RecursiveGetExtendedObjects(currentObject, includedObjects);

    //Add the objects to a list
    IObjectList newInstances = EcoServiceHelper.GetVariableFactoryService(objectList[0]).CreateUntypedObjectList(true);
    foreach (KeyValuePair kvp in includedObjects)
      newInstances.Add(kvp.Key);

    //Return the constraints from ModeledConstraintProvider
    ModeledConstraintProvider.GetConstraintsForObjects(newInstances, constraints);
  }

  private void RecursiveGetExtendedObjects(IObject currentObject, Dictionary includedObjects)
  {
    //Don't process the same object twice
    if (includedObjects.ContainsKey(currentObject))
      return;

    includedObjects.Add(currentObject, null);

    //If the class implements IValidationExtender then add its constrained objects
    IValidationExtender extender = currentObject.AsObject as IValidationExtender;
    if (extender != null)
    {
      foreach (IObject dependentObject in extender.GetConstraintedObjects())
        RecursiveGetExtendedObjects(dependentObject, includedObjects);
    }
  }
}




Step 03: Register the service in the EcoSpace

public InteevoWebsiteEcoSpace(): base()
{
  InitializeComponent();
  RegisterEcoService(typeof(IConstraintProvider), new ExtendedConstraintProvider());
}



Now I can validate a list of dirty objects using EcoSpace.GetEcoService().GetConstraintsForObjects.


Step 04: Last point of defence, ensure that no invalid objects may be saved. Only relevant methods are shown.

internal class ValidatingPersistenceService : IPersistenceService
{
  private IPersistenceService Inner;
  private IEcoServiceProvider ServiceProvider;

  internal ValidatingPersistenceService(IEcoServiceProvider serviceProvider)
  {
    if (serviceProvider == null)
      throw new ArgumentNullException("serviceProvider");

    ServiceProvider = serviceProvider;
    Inner = ServiceProvider.GetEcoService();
    if (Inner == null)
      throw new ArgumentException("ServiceProvider did not provide an instance for IPersistenceService");
  }

  private IConstraintProvider constraintProvider;
  private IConstraintProvider ConstraintProvider
  {
    get
    {
      if (constraintProvider == null)
      {
        constraintProvider = ServiceProvider.GetEcoService();
        if (constraintProvider == null)
          throw new InvalidOperationException("IConstraintProvider not registered as an ECO service");
      }
      return constraintProvider;
    }
  }



  void IPersistenceService.UpdateDatabaseWithList(IObjectList list)
  {
    ValidateObjects(list);
    Inner.UpdateDatabaseWithList(list);
  }

  private void ValidateObjects(IObjectList objects)
  {
    List constraints = new List();
    ConstraintProvider.GetConstraintsForObjects(objects, constraints);
    foreach (DroopyEyes.EcoExtensions.Validation.IConstraint currentConstraint in constraints)
    {
      if (!currentConstraint.IsValid)
      {
        throw new InvalidOperationException(
          string.Format("Cannot update database with invalid objects:\r\n{0} : {1}",
            currentConstraint.Instance.UmlClass.Name, currentConstraint.Name)
        );
      }
    }//foreach constraint
  }
}



Step 05: Replace the standard IPersistenceService in the EcoSpace

public InteevoWebsiteEcoSpace(): base()
{
  InitializeComponent();
  RegisterEcoService(typeof(IPersistenceService), new ValidatingPersistenceService(this));
  RegisterEcoService(typeof(IConstraintProvider), new ExtendedConstraintProvider());
}



Finally I have an implementation which does the following

A: Allows me to get constraints for dirty objects + all relevant objects
B: Prevents the app from saving objects with broken constraints.

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