Monday, October 04, 2004 - Posts

Interesting Topics on Domain Repositories

posted Monday, October 04, 2004 2:48 PM by mlorengo

I've been following some interesting posts about Domain Driven Design. Steve Maine's has expanded on his initial posts about creating a Repository. His latest post uses the idea of an Associate class sparked by Steve Eichert's post to allow for the saving of root aggregates from within one another. He's implementing is approach in VS2005 using Generics and Partial Classes. This latest flurry of posts got me thinking about my current architecture for the Virtual Cellar.

As you may recall, my initial design allowed me to write some code like this

ProducerGateway pg = VirtualCellarManager.GetProducerGateway();
Producer p = new Producer( "Hightower Cellars" );
pg.Add( p );
// Lookup the producer by the ID
Producer p2 = pg.FindByID( p.ID );
WineGateway wg = VirtualCellarManager.GetWineGateway();
Wine w = new Wine( 2001, "Cabernet Sauvignon" );
//Add the wine for the producer
wg.Add( p2, w );
// or I could do something like this
p2.Wines.Add( w );

After looking at the posts, I thought to me self, self what would it look like under this new model

RepositoryFactor rf = new RepositoryFactory();
IRepository r = rf.GetRepository( typeof(Producer) );
Producer p = Producer.Factory.Create( "Hightower", rf );
r.Save(p);
// Lookup the producer by the ID
Producer p2 = r.Load( p.ID );
Wine w = Wine.Factory.Create( 2001, "Cabernet Sauvignon", rf );
p2.Wines.Add( w );

This isn't much different codewise, but it will give me some power as later on I can begin to ask for repositories based on the object's type rather than "hardcoding" the type. For example

Producer p = Producer.Factory.Create( "Columbia Winery" );

IRepository r = rf.GetRepository( p.GetType() );

So, I've begun creating NUnit Tests for my RepositoryFactory class. Here's what I've come up with

/// <summary>
/// Tests to make sure a ProducerRepository is returned
/// </summary>
[Test]
public void GetRepositoryForProducer()
{
	IRepository r = _rf.GetRepository( typeof(Producer) );
	Assert.AreEqual( typeof( Lorengo.VirtualCellar.Business.ProducerRepository), r.GetType() );
}

/// <summary>
/// Test to make sure an exception is thrown when a null type is passed
/// </summary>
[Test]
[ExpectedException( typeof(ArgumentNullException) )]
public void GetRepositoryForNull()
{
	IRepository r = _rf.GetRepository( null );
}

/// <summary>
/// Tests to make sure an exception is thrown when a invalid type is passed
/// </summary>
[Test]
[ExpectedException( typeof(ArgumentOutOfRangeException) )]
public void GetRepositoryForInvalidType()
{
	IRepository r = _rf.GetRepository( typeof(RepositoryFactory) );
}

So, I have a question, is the ArgumentOutOfRangeException, the correct exception to throw in this case? Or is there another Exception that better matches the fact that no Repository exists for the System.Type being passed in?

 

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