March 31, 2009 No comments







WindsorBootstrapper for Prism2

For a large, enterprise application at work, I have been utilizing the Prism (CompositeWPF) framework. The application is still in progress, so I am unable to discuss it’s nature too much in detail. However, Prism has been a large help in getting the base framework for the application laid out and constructed. After finishing a few other tasks, I decided to check the status of the CompositeWPF project and look for any updates. That day just happened to coincide with Prism2′s latest release. The update sounded appealing, so I started the process of moving everything over to it.

While moving over to the February 2009 release of Prism2, I ran into issues with a few of the pieces I was using from the CompositeWPFContrib project. For example, the Windsor container bootstrapper had not been updated for the new release of Prism, leading to many problems. In order to fully move over to Prism2, I’d need to either give up on using Windsor, or create a new bootstrapper for Prism2 capable of working with Castle Windsor. Choosing option 2, I started with the bootstrapper for Unity and with the base Castle Windsor implementation for ServiceLocator, then modified them quite a bit. The final results that I ended up with will be posted below.

One significant difference between Castle Windsor and Unity came to light while writing and testing these new classes. If a specific instance of a class that hasn’t been registered into the container is requested from Unity, Unity doesn’t complain and just goes ahead and injects what is needed. Castle Windsor, on the other hand, will throw an exception complaining that the component wasn’t registered. Both seem like valid approaches, but I wanted to make the transition as simple as possible. So, to avoid changing too much of the logic found within Prism2 (and the bootstrapper), I added a “ResolveEx” extension function to IWindsorContainer. If a specific class is requested through this function that isn’t in the container, it will register it as transient and return an instance. I also changed the ServiceLocator implementation for Castle Windsor to use “ResolveEx” if a key is not passed in.
Read the rest of this entry »

February 18, 2009 No comments





Castle ActiveRecord and Fluent Create/Update/Save

I came up with an interesting idea the other day at work involving some work I had been doing with Castle ActiveRecord. I am using (a modified) GeneratorStudio to produce ActiveRecord partial classes based on a database schema that I have. All of my code additions go into another set of partial class files so that I can regenerate the base classes whenever I need to.

However, there are many times when I need to find a specific item, and if it isn’t found, I need to create a new one. After this, it is used for yet another item. So essentially, the item has to exist before the code can continue. This is where my slightly clever (if I can call it that) idea comes into play.

I will be using part of the example Post class from http://www.castleproject.org/ActiveRecord/gettingstarted/classes.html as a basis for the new idea:

[ActiveRecord]
public class Post : ActiveRecordBase<Post>
{
    private int id;
    private String title;
 
    public Post()
    {
        created = DateTime.Now;
    }
 
    [PrimaryKey]
    public int Id
    {
        get { return id; }
        set { id = value; }
    }
 
    [Property]
    public String Title
    {
        get { return title; }
        set { title = value; }
    }
}

For all of my unique indexes, I create additional static helper methods that allow retrieval by those constraints. Let us assume that Title is a unique index; that is, there can only be a single post with a specific title. Then the following function becomes valid (in the Post class):

public static Post GetByTitle(string title)
{
    return FindOne(Restrictions.Eq("Title",title));
}

And here is my little idea for making a small fluent addition (to the Post class):

public Post CreateFluent()
{
    Create();
    return this;
}

A function similar to this would hopefully work for CreateAndFlush, Update, UpdateAndFlush, Save, and SaveAndFlush as well. Once all of this is in place, I now have many new options for dealing with items that need to exist or be updated before they can be used. I find the fluent-like style of this to be easy to read while working through code:

var post = Post.GetByTitle("42") ?? new Post { Title = "42" }.CreateFluent();
 
// do something important with post

Since Post.GetByTitle(string title) will return null if the post cannot be found, the null coalescing operator (??) takes care of automatically running the second half and creating the new Post if a Post with the specified title couldn’t be found. I’m still testing this fully to see how well it works, but I’ll update here once I get concrete evidence of its functionality.

EDIT: I’ve been using this for the last few weeks and I have not run into any issues with it. It looks pretty slick in the code, too.

Recent Posts

Categories

Blogroll