Ayende @ Rahien

Scott Muc commented on Who is the responsible party?

Wed, 20 May 2009 04:07:27 GMT

@Dave I would have other validation logic in there. To create a bad example, what if a parent is not allowed to have 0 children? I would have a remove method on the Parent class because it's a business rule that says a Parent must have at least one child. I understand what you're saying though, and I like your code sample. Just trying to bring up an alternative form.

Peter Morris commented on Who is the responsible party?

Tue, 19 May 2009 09:15:07 GMT

I wouldn't have thought this was a tell-don't-ask scenario. I'd have said it was more a connascence of algorithm.

Ayende Rahien commented on Who is the responsible party?

Tue, 19 May 2009 07:47:08 GMT

Tariq, That is call Command pattern, and it is fairly common way to deal with externalizing the logic while keeping it close.

Dave commented on Who is the responsible party?

Tue, 19 May 2009 07:11:52 GMT

@Scott. Why create (and introduce) a new method? Are you also adding a Get and Delete method? If so, you're violating the S in the SOLID principle where a class should have only one (single) responsibility. I guess you already have a collection of children. So why not override the Add itself. public class ChildCollection : List

Scott Muc commented on Who is the responsible party?

Tue, 19 May 2009 06:07:16 GMT

What about the following? parent.AddChild(child); where:: public virtual void AddChild(Person child) { child.Parent = this; this.children.Add(child); }

Tariq commented on Who is the responsible party?

Mon, 18 May 2009 23:53:19 GMT

So then how does that explain for instance the reason for some people creating an ObjectTask class which would do some additional functionality related to the behaviour(e.g CartTask.AddToCart(Cart cart, Item someItem) where CartTask would calculate and set shipping or log history or any additional tasks) shouldnt these be handled by the AddtoCart function?

Ayende Rahien commented on Who is the responsible party?

Mon, 18 May 2009 19:32:23 GMT

Bidi collections tend to cause a lot of problems in the long run

Jason Y commented on Who is the responsible party?

Mon, 18 May 2009 19:23:14 GMT

It is possible (though not necessarily easier) to place logic in collection classes and properties so that parent.Children.Add(child); // Children is a custom collection child.Parent = parent; // Parent is a property, not a field does _not_ violate Tell, Don't Ask because the Parent and ChildCollection classes (and any classes derived from them) implement all the logic. .NET does this repeatedly, I think.

Joe commented on Who is the responsible party?

Mon, 18 May 2009 18:20:50 GMT

This is one of the big reasons why I like NHiberate, the parent can easily hide the underlying children collection and dictate how you get at and set its children. Most other ORMs that I have been exposed to (not naming names to avoid a flame war) makes the children collection public on the parent and does not offer a way of controlling access to the collection.

Ayende Rahien commented on Who is the responsible party?

Mon, 18 May 2009 18:06:42 GMT

Scott, The question is, who is responsible for doing so

Scott White commented on Who is the responsible party?

Mon, 18 May 2009 17:35:20 GMT

There are times you have to set a children's parent, such as when using a foreign generator in NHib with 1 to 1 relationships and you want to propagate save-update.