DDD – the coin drops for Marcus

February 17, 2009

I have now tried to grasp the DDD-concept without fully “getting it”. I must confess that I have thought: “What is the deal with this… I have done it before”.

But today we had a most prominent guest at Elevate (the education initiative at Avega) – Jimmy Nilsson.  And what he said got the coin to drop for me.

The heading of his presentation was something like “A new era for data access”. And the things he said that got me to understand was something like this – not a quote but rather his reasoning:

Traditionally we focus on the database design in application development. So very early we want to get the database design in place. “We need it to start to do code”. Since we did that design early in the process we often got it wrong and inherited those error through the process. And...

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Simple but useful generic repository pattern

February 16, 2009

I have pointed here several times before – but it’s so nice.

It’s an implementation of the Repository Pattern using generics, that will minimize your code in a very nice way. I am sure that the FindAll can be refined into something very nice with LINQ, that allows you to send a specification criteria or so.

Here is my implementation that uses a common interface (IBaseEntity) for all my entities. It basically has an ID, so that the abstract implementation can use it as a key:

namespace Marcusoft.SprintPlannerHelper.Repositories { /// \<summary\> /// A generic repository interface that dictates all the methods that a repository should map to /// \</summary\> /// \<typeparam name="T"\>the type of the interface\</typeparam\> public interface IRepository<T>  where 

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Sprint Planner Helper – Session 10

February 16, 2009

You could call the last session my first “sprint demo.” What happened was that I could finally see where this was going. As the Product Owner, I was not happy – I couldn’t even yell at the team (also me) because the result was quite poor.

What Went Wrong

Firstly, I was not happy that certain actions were only available to specific roles (e.g., “As Product Owner,” “As Scrum Master”). I want the Sprint Planner Helper to be open and useful without hindering you with role checks.

Secondly, I was too detailed in my model. For instance, why bother with a ProductOwnerController when it’s just an attribute on the ProductBacklog? The same applies to the Product attribute.

The Solution

I had a meeting with the team, designer, and domain experts (in this case, me on all three accounts) to do some domain...

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Sprint Planner Helper – Session 9

February 15, 2009

Today I focused on finally getting the controller for my Product Owner tested and done.

For now, the controller will always use my test data repository so that I will know the state of the data. I really want to create my first view also – which will be that list of products.

Look at this really nice feature that helps you create views with the ASP.NET MVC kit.

This promises great things for the final release. More to read about this in this post by the Gu.

Oh yeah – my first view is realized…

At this point, I also realized two things: I will need to sketch out the GUI and I will be needing to add products, product owner, and backlog. So I will probably rip the generic template for repositories from here.

But … hey – my first view! Me so proud. Me want...

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Sprint Planner Helper – Session 8

February 12, 2009

This hour almost entirely was reading. I didn’t not feel comfortable yet with terms Repository and Service, or how they relate to each other.

Also I feel that I have looked to much at the architecture of ASP.NET MVC Storefront Starter Kit. I have incorporated stuff that I didn’t thought to much about – stupid, but I did it anyway.

But after a while I found this introduction to DDD and it explained some things for me. Here is how I understand the two fore-mentioned concepts:

  • A Repository are classes and methods that is used to load stuff from a data store. They are often written in a way that is easily mocked or replaced during testing.
  • A Service is used to hold a process or a flow through a business logic that does not fit well on a class in the domain model. They are stateless...
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Sprint Planner Helper – Session 7

February 11, 2009

I’ve been doing some major reworking of the repository that I am using, from being a product repository to being a ProductOwnerRepository and a ProductBacklogRepository. This took me more than one hour and therefore I did it as a prolonged check-out session.

Halfway through that prolonged session, I realized that I still don’t quite get the repository pattern (by the way, here is a great post about the repository pattern) or rather the way it’s being used in the ASP.NET MVC Storefront Starter Kit. The thing that had me confused is the service… It feels like an extra layer on top of the repository that I don’t understand.

But 06:03 into part 8 of the video series, I got it… What Rob Conery is doing is to overload the constructor of the controller so that he can send in a fake version...

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Sprint Planner Helper – Session 6

February 9, 2009

OK – I did some reading about repositories, and they basically constitute a way for the domain model to perform CRUD operations – in a language needed by the domain model.

This great document provides an example and some very good explanations on what the difference between an Entity (has an ID), a Value Object (doesn’t have an ID in the model), and Aggregates (things that consist of other things) are.

So today I’ll back up and create a repository that can retrieve the products for a product owner – the IProductRepository. I am test-driving it forward, of course.

After a while…

Oh yeah – I love the way TDD is leading me forward. Really nice code is emerging.

I didn’t get quite as far as I hoped. I was hoping to be able to code a bit of controller-action (hehe…) today. Well – tomorrow maybe.

...
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Norwegian Championships – the aftermath

February 9, 2009

OK – my guess wasn’t completely off (got the first right, didn’t I). Oslo Brass Band shocked by coming second in their first year in the championship section. Since I have played with a few of the bandsmen (and women) in that band, I was really proud. Well done – Tone, Mattias, and Clare!

Also, Eikanger has my favorite euphonium player – Patrik Randefalk – and he and the rest of the band were marvelous, especially on the Extreme Makeover.

But the thing that impressed me most was that the whole event was taped for Norwegian television. You can see every performance afterwards here.

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Sprint Planner Helper – Session 5

February 8, 2009

OK – this was a really short session and it also marks the end of the first week of the project. Five hours a week – I’d love to work with this all the time…

I managed to get around the understanding of controllers. This article was a great help… BUT they have changed some stuff. So, in order to get hold of the actual model in a view you now (ASP.NET MVC RC 1) need to go:

[TestMethod] public void indexViewModelIsAProductListWithOneElementsForTheTestUser() { var c = new ProductOwnerController(); var view = c.Index() as ViewResult; var model = (List<Product>) view.ViewData.Model; Assert.AreEqual(1, 

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Snippet for creating test method in C#

February 8, 2009

Here is a short snippet that saves me a lot of time. It simply creates a test method with the correct attributes and stuff. Simply but useful – and now you don’t have to write it. <?xml version=”1.0” encoding=”utf-8” ?> <Header> TestMethod tm Code snippet for creating a test method Marcusoft (www.marcusoft.net) Expansion SurroundsWith </Header> methodName The name of the test methodName <![CDATA[<TestMethod()> _ public void should_$methodName$() { // Arrange // Act // Assert Assert.Fail("Implement test"); }]]>

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