I'm trying to develop an application using the MVP pattern.
The problem is wiring all the code manually. I was hoping to reduce the code needed. I tried to copy another solution, but I couldn't get to work. I'm using Winforms and the solution I was using as source is using WPF.
It would wire things on some conventions:
View events are wired by name. For example:"Loaded" event on the view will be wired to the "OnLoaded()" method on the presenter Button commands are wired by name. For example: MoveNext" button is wired to the "OnMoveNext()" method. Grids double click is wired by name. For example: Double click on "Actions" will be wired to the "OnActionsChoosen(ToDoAction)"
The working code in WPF is:
private static void WireListBoxesDoubleClick(IPresenter presenter)
{
var presenterType = presenter.GetType();
var methodsAndListBoxes = from method in GetActionMethods(presenterType)
where method.Name.EndsWith("Choosen")
where method.GetParameters().Length == 1
let elementName = method.Name.Substring(2, method.Name.Length - 2 /*On*/- 7 /*Choosen*/)
let matchingListBox = LogicalTreeHelper.FindLogicalNode(presenter.View, elementName) as ListBox
where matchingListBox != null
select new {method, matchingListBox};
foreach (var methodAndEvent in methodsAndListBoxes)
{
var parameterType = methodAndEvent.method.GetParameters()[0].ParameterType;
var action = Delegate.CreateDelegate(typeof(Action<>).MakeGenericType(parameterType),
presenter, methodAndEvent.method);
methodAndEvent.matchingListBox.MouseDoubleClick += (sender, args) =>
{
var item1 = ((ListBox)sender).SelectedItem;
if(item1 == null)
return;
action.DynamicInvoke(item1);
};
}
}
private static void WireEvents(IPresenter presenter)
{
var viewType = presenter.View.GetType();
var presenterType = presenter.GetType();
var methodsAndEvents =
from method in GetParameterlessActionMethods(presenterType)
let matchingEvent = viewType.GetEvent(method.Name.Substring(2))
where matchingEvent != null
where matchingEvent.EventHandlerType == typeof(RoutedEventHandler)
select new { method, matchingEvent };
foreach (var methodAndEvent in methodsAndEvents)
{
var action = (Action)Delegate.CreateDelegate(typeof(Action),
presenter, methodAndEvent.method);
var handler = (RoutedEventHandler)((sender, args) => action());
methodAndEvent.matchingEvent.AddEventHandler(presenter.View, handler);
}
}
private static IEnumerable<MethodInfo> GetActionMethods(Type type)
{
return from method in type.GetMethods(BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.Instance)
where method.Name.StartsWith("On")
select method;
}
private static IEnumerable<MethodInfo> GetParameterlessActionMethods(Type type)
{
return from method in GetActionMethods(type)
where method.GetParameters().Length == 0
select method;
}
Anyway, I tried to port that to a WinForm app, but I wasn't successful. I changed the RoutedEventHandlers to EventHandlers, but couldn't find what to do about the LogicalTreeHelper.
I'm kind of stuck on this. I could do manually but I found this mini-framework so ingenuous that it's almost crazy.
PS: Source is http://msdn.microsoft.com/en-us/magazine/ee819139.aspx
Edit
I just realized something. I'm not gone dumb, the code above is not very test friendly, is it?
Ok. I got it working myself. I'm just posting the answer because at lest one other person found interesting.
First, the view
public interface IBaseView
{
void Show();
C Get<C>(string controlName) where C : Control; //Needed to later wire the events
}
public interface IView : IBaseView
{
TextBox ClientId { get; set; } //Need to expose this
Button SaveClient { get; set; }
ListBox MyLittleList { get; set; }
}
public partial class View : Form, IView
{
public TextBox ClientId //since I'm exposing it, my "concrete view" the controls are camelCased
{
get { return this.clientId; }
set { this.clientId = value; }
}
public Button SaveClient
{
get { return this.saveClient; }
set { this.saveClient = value; }
}
public ListBox MyLittleList
{
get { return this.myLittleList; }
set { this.myLittleList = value; }
}
//The view must also return the control to be wired.
public C Get<C>(string ControlName) where C : Control
{
var controlName = ControlName.ToLower();
var underlyingControlName = controlName[0] + ControlName.Substring(1);
var underlyingControl = this.Controls.Find(underlyingControlName, true).FirstOrDefault();
//It is strange because is turning PascalCase to camelCase. Could've used _Control for the controls on the concrete view instead
return underlyingControl as C;
}
Now the Presenter:
public class Presenter : BasePresenter <ViewModel, View>
{
Client client;
IView view;
ViewModel viewModel;
public Presenter(int clientId, IView viewParam, ViewModel viewModelParam)
{
this.view = viewParam;
this.viewModel = viewModelParam;
client = viewModel.FindById(clientId);
BindData(client);
wireEventsTo(view); //Implement on the base class
}
public void OnSaveClient(object sender, EventArgs e)
{
viewModel.Save(client);
}
public void OnEnter(object sender, EventArgs e)
{
MessageBox.Show("It works!");
}
public void OnMyLittleListChanged(object sender, EventArgs e)
{
MessageBox.Show("Test");
}
}
The "magic" happens at the base class. In the wireEventsTo(IBaseView view)
public abstract class BasePresenter
<VM, V>
where VM : BaseViewModel
where V : IBaseView, new()
{
protected void wireEventsTo(IBaseView view)
{
Type presenterType = this.GetType();
Type viewType = view.GetType();
foreach (var method in presenterType.GetMethods())
{
var methodName = method.Name;
if (methodName.StartsWith("On"))
{
try
{
var presenterMethodName = methodName.Substring(2);
var nameOfMemberToMatch = presenterMethodName.Replace("Changed", ""); //ListBoxes wiring
var matchingMember = viewType.GetMember(nameOfMemberToMatch).FirstOrDefault();
if (matchingMember == null)
{
return;
}
if (matchingMember.MemberType == MemberTypes.Event)
{
wireMethod(view, matchingMember, method);
}
if (matchingMember.MemberType == MemberTypes.Property)
{
wireMember(view, matchingMember, method);
}
}
catch (Exception ex)
{
continue;
}
}
}
}
private void wireMember(IBaseView view, MemberInfo match, MethodInfo method)
{
var matchingMemberType = ((PropertyInfo)match).PropertyType;
if (matchingMemberType == typeof(Button))
{
var matchingButton = view.Get<Button>(match.Name);
var eventHandler = (EventHandler)EventHandler.CreateDelegate(typeof(EventHandler), this, method);
matchingButton.Click += eventHandler;
}
if (matchingMemberType == typeof(ListBox))
{
var matchinListBox = view.Get<ListBox>(match.Name);
var eventHandler = (EventHandler)EventHandler.CreateDelegate(typeof(EventHandler), this, method);
matchinListBox.SelectedIndexChanged += eventHandler;
}
}
private void wireMethod(IBaseView view, MemberInfo match, MethodInfo method)
{
var viewType = view.GetType();
var matchingEvent = viewType.GetEvent(match.Name);
if (matchingEvent != null)
{
if (matchingEvent.EventHandlerType == typeof(EventHandler))
{
var eventHandler = EventHandler.CreateDelegate(typeof(EventHandler), this, method);
matchingEvent.AddEventHandler(view, eventHandler);
}
if (matchingEvent.EventHandlerType == typeof(FormClosedEventHandler))
{
var eventHandler = FormClosedEventHandler.CreateDelegate(typeof(FormClosedEventHandler), this, method);
matchingEvent.AddEventHandler(view, eventHandler);
}
}
}
}
I've got this working here as it is. It will autowire the EventHandler on the Presenter to the Default Events of the Controls that are on IView.
Also, on a side note, I want to share the BindData method.
protected void BindData(Client client)
{
string nameOfPropertyBeingReferenced;
nameOfPropertyBeingReferenced = MVP.Controller.GetPropertyName(() => client.Id);
view.ClientId.BindTo(client, nameOfPropertyBeingReferenced);
nameOfPropertyBeingReferenced = MVP.Controller.GetPropertyName(() => client.FullName);
view.ClientName.BindTo(client, nameOfPropertyBeingReferenced);
}
public static void BindTo(this TextBox thisTextBox, object viewModelObject, string nameOfPropertyBeingReferenced)
{
Bind(viewModelObject, thisTextBox, nameOfPropertyBeingReferenced, "Text");
}
private static void Bind(object sourceObject, Control destinationControl, string sourceObjectMember, string destinationControlMember)
{
Binding binding = new Binding(destinationControlMember, sourceObject, sourceObjectMember, true, DataSourceUpdateMode.OnPropertyChanged);
//Binding binding = new Binding(sourceObjectMember, sourceObject, destinationControlMember);
destinationControl.DataBindings.Clear();
destinationControl.DataBindings.Add(binding);
}
public static string GetPropertyName<T>(Expression<Func<T>> exp)
{
return (((MemberExpression)(exp.Body)).Member).Name;
}
This eliminates "magic strings" from the Binding. I think it can also be used on INotificationPropertyChanged.
Anyway, I hope someone finds it useful. And I completely ok if you want to point out code smells.
来源：https://stackoverflow.com/questions/13635503/wiring-view-model-and-presenter-dynamically-by-convention-reflection