Fat Agnus

The Common Service Locator (CSL) is a helpful library and at first sight it might look like some new cool thing that you need, but it really depends on what you are trying to build.

Do I need it?

Typically, the answer to this question is no. Once you’ve decided on a container that suits your project, there’s not a whole lot of benefit from writing your whole application in a way that can switch containers. – The CSL Wiki

The library will just provide you with an extra layer of abstraction and is only meant for people who are building frameworks where there is a need for allowing people to specify what kind of DI (dependency injection) container they want to use, so that they aren’t tied down to using a specific implementation made by the authors.

Using the library and creating the adaptor

There are a few ways to have the adapter implement the interface. You can either use the IServiceLocator interface or you can use ServiceLocatorImplBase, which is used as a convenience for those who wants to implement the IServiceLocator interface.

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public class MyServiceLocatorAdapter : ServiceLocatorImplBase
{
    private IMyContainer container;
 
    public MyServiceLocatorAdapter(IMyContainer container)
    {
        this.container = container;
    }
 
    protected override object DoGetInstance(Type serviceType, string key)
    {
        return container.Resolve(serviceType, key);
    }
 
    protected override IEnumerable<object> DoGetAllInstances(Type serviceType)
    {
        return container.ResolveAll(serviceType);
    }
}

You only need to implement the two protected methods and then you are good to go. Now you are ready create your own adapter, but you can also find a few that has already been written.

Setting it up

I have changed the above example a bit, so that it will take a UnityContainer.

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IUnityContainer container = new UnityContainer();
container.RegisterType<ISomeRepository, SomeRepository>();
 
MyServiceLocatorAdapter locator = new MyServiceLocatorAdapter(container);
 
ServiceLocator.SetLocatorProvider(() => locator);
 
ISomeRepository repository = ServiceLocator.Current.GetInstance<ISomeRepository>();;

Finale word

There are of course already a few online, so you might as well take advantage of them instead of starting from scratch.

If you are going to use this, make sure you check out this blog first because there are a few pitfalls that you need to be aware of.

Further reading

How to setup the Unity Container

Common Service Locator Wiki

In a previous article I gave an example of how powerfull the SmartDispatcherController can be, but you can do a lot more with it. You can actually map your Json objects to your objects in the C# code, when you parse it to one of your actions.

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public struct JSONObject
{
	public string Var1;
	public string Var2;
	public int[] Var3;
}

There is nothing new here, so moving on.

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new Ajax.Request("/base/testJSON.rails", { 
   method: 'post',
   parameters: { JSONObject: Object.toJSON( {Var1: 'Hello World', 
                                            Var2: 'Something else', 
                                            Var3: [1,2,4]} ) },
   onSuccess: function(transport) { 
      alert(transport.responseText);
   }
});

If you are new to Prototype, this might look a bit strange, but what it basically does is that it makes an ajax request and parse a Json object as the parameter.

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public void testJSON([JSONBinder("JSONObject")] JSONObject myJsonObject)
{
	// Do something
}

The biggest change here, from my previous example, is that instead of using the DataBind attribute, we apply the JSONBinder attribute.

If you want to try this out, then you should reference the Castle.MonoRail.JSONSupport.dll and the Newtonsoft.Json.dll. The last one can be found in the external-dependencies.zip file.

Yet another great video from Douglas Crockford

http://video.yahoo.com/video/play?vid=1382941

And here is a little bonus video

Browser Wars Episode II: Attack of the DOMs