Friday, April 18, 2008

Unity Explained

I had some time in the night to make use of the MS Unity applcation block, and I thought of writting a post on an example written uing Unity.
To use the dependency injection in your code via Unity is just 2 steps.
1) Create an instance of the Unity container, like this.
//Import UnityContainer container = new UnityContainer();
UnityContainer container = new UnityContainer();


2) Register your type with the Unity container. This can be done through a configuration file or thorugh code, for our example we are using the latter approach.
container.RegisterType <IService, ServiceImpl>();

3) Get the required instance from the container, using the Resolve()
DisplayClass display = container.Resolve<DisplayClass>();

The complete code example is as follows :

using System;

using Microsoft.Practices.Unity;
using Microsoft.Practices.ObjectBuilder2;
namespace unity1

{
class Program
{
static void Main(string[] args)
{
//Create the container
UnityContainer container = new UnityContainer();

//Register the our type
container.RegisterType <IService, ServiceImpl>();

//Get an instance of our type NOTE : an instance of ServiceImpl
//will in be constructor injected into the DisplayClass when it is created

DisplayClass display = container.Resolve<DisplayClass>();

display.Show();
}
}

public interface IService
{
void Show();
}

public class ServiceImpl : IService
{
public void Show()
{
Console.WriteLine("In ServieImpl Show()");
}
}

public class DisplayClass
{

private IService srv;
public DisplayClass(IService srv)
{
this.srv = srv;
}

public void Show()
{
srv.Show();
}
}
}

In this example you can see that the ServiceImple class impliments the IService interface and we register this type with the container in our
main method, also you can see that the Display class's constructor takes an instance of IService.
In our main method we create an instance out of the DisplayClass using the Resolve method of the container and whats nice is that an instance of IService is created by the container and used to instansiate the DisplayClass.

3 comments:

  1. You might want to double check your post - it looks like it ate all the angle brackets for the generic methods which makes things a little hard to follow.

    ReplyDelete
  2. Ye, you are correct, The code was a direct copy-past from a a running program, but I am not sure why the angel brakets did not show up...
    I'll rectify the post soon...

    ReplyDelete
  3. Ok the formating is done. Thank for the info Chris...

    ReplyDelete