Zen and the art of Castle maintenance

The more I push this thing into broader scenarios, the more I’m disappointed. The biggest flaw lies within its interaction with FormHelper under some scenarios. For example, you can have an entity like

public class Order
{
  private Customer owner;

  public Customer Owner
  {
    ...
  }
}

public class Customer
{
  private int id;

  public int ID
  {
    ...
  }
}

So far, so good. Now suppose you want to render a form where the Order’s owner can be changed. You’d use a select form element to do that. You also demand that an order has an owner so you use the ValidateNonEmpty attribute:

public class Order
{
  private Customer owner;

  [ValidateNonEmpty]
  public Customer Owner
  {
    ...
  }
}

And now you render the form using the FormHelper to have the “auto-wired” validation:

$Form.FormTag("%{action='SaveOrder'}")

$Form.HiddenField("order.id")

$Form.LabelFor("order.owner.id", "Owner:")
$Form.Select("order.owner.id", $customers, "%{text='Name', value='Id'}")

$Form.EndFormTag()

As you see we have to bind the Owner.ID property, so when the DataBinder starts to populate the Order instance it will instantiate a new Customer class and fill the ID property with whatever was chosen on the select form element. The good news that we kept the validation logic in a declarative format, and tight to our domain model, instead of scattering it throughout the layers. The bad new is that it doesn’t work.

“Why?” - you might ask. Fair question. The responsible to output the validations is the FormHelper. It works collaboratively with the ValidatorRunner to collect and apply the validations as it navigates through the properties. Using our example:

$Form.Select("order.owner.id", $customers, "%{text='Name', value='Id'}")

In this case the FormHelper will try to collect validators for the ID property. And obviously it won’t find anything useful there.

Possible solutions?

Collect the validators in a chain

Using the same example:

$Form.Select("order.owner.id", $customers, "%{text='Name', value='Id'}")

If we use a chain, the FormHelper could try to grab validators (using the runner) for the Owner property and then for the Id property, which, in this case, would result in the expect behavior.

The first time I thought about this solution I quickly bumped into a situation that invalidated it. However I can’t remember it. So, assuming that people that read this entry to this point have a brain bigger that this pea-sized brain here, would you mind sparing a minute of thinking to check if my solution would be enough or if there’s a better alternative? Thanks in advance!