How would you implement a MVP schema in your user interface?
For each page or Windows form you may have consider the following. As your first step, you define the interface that represents the view. It is the contract between view and presenter and the conduit of communication between the two. Here's an example:
namespace Samples.Basic {
public interface IScreenView {
DateTime Now { set; }
}
}
The View interface mostly needs setters for properties since it just needs to show the model. The Presenter is a class responsible for getting any data to pass along to the view and it also provides one method for each action the user can accomplish on the screen.
public class ScreenPresenter {
private IScreenView view;
public ScreenPresenter(IScreenView view)
{
this.view = view;
}
public void Initialize()
{
view.Now = DateTime.Now;
}
}
Upon initialization, the presenter receives a reference to the view and initializes the view by setting all of its public members in the contract. Hence, the view once received data takes the time to reflect that data in the real user interface — controls. Still feeling lost? Read on and consider an ASP.NET page with just one Label control in its user interface.
<asp:label runat="server" id="lblCurrentTime" />
Here's a code-behind class for this page that is respectful of the MVP pattern.
public class Samples_Screen : System.Web.UI.Page, IScreenView
{
protected void Page_Load(object sender, EventArgs e)
{
ScreenPresenter presenter = new ScreenPresenter(this);
presenter.Initialize();
}
public DateTime Now
{
set { lblCurrentTime.Text = value.ToString(); }
}
}
Do you really think this is hard stuff? Sure, the example is straightforward, but the underlying ideas and models are the same regardless of the richness of the view. Where's the benefit? You neatly separate view from the logic behind. And can easily use the same logic of gathering data to populate a radically different user interface. For example, a classic ASP.NET and an AJAX user interface.
