After a lot more thinking about this, I've come up with a really neat solution, needs more testing, but here it is in current form. There's a MessageSender and MessageReceiver class which between them handle sending InitMessageBase type objects and allow buffering and requesting of a message if target is not constructed.
Example code here
Part 1 here
MessageSender
public class MessageSender<T> where
T : InitMessageBase
{
private T _message = default(T);
public MessageSender()
{
// Send back item when a constructor asks for it
Messenger.Default.Register<T>(this, message =>
{
if (this._message
!= null && this._message
!= message && !this._message.Received)
{
// Send back original message
Messenger.Default.Send(this._message);
}
});
}
public void
SendMessage(T message)
{
// Store value
this._message = message;
// Try and send message
Messenger.Default.Send(message);
}
}
MessageReceiver
public class MessageReceiver<T> where T : InitMessageBase
{
private Action<T>
_handler = null;
private T _message = null;
public MessageReceiver(Action<T>
handler)
{
this._handler = handler;
// Wait for messages
Messenger.Default.Register<T>(this, message =>
{
if (this._message
!= null && this._message
!= message && !message.Received)
{
message.Received = true;
this.OnMessageReceived(message);
}
});
}
/// <summary>
/// Send empty message on
instantiation
/// </summary>
/// <param name="message"></param>
public MessageReceiver(Action<T>
handler, bool sendInitMessage)
:
this(handler)
{
if (sendInitMessage)
{
this._message
= Activator.CreateInstance(typeof(T))
as T;
// Send empty message
Messenger.Default.Send<T>(this._message);
}
}
private void
OnMessageReceived(T message)
{
if (this._handler != null)
this._handler(
message );
}
}
InitMessageBase
public abstract class InitMessageBase : MessageBase
{
// Used for a send
public bool Received
{ get; set; }
public InitMessageBase()
{
}
}
An Implementation of InitMessageBase
public class ArticleInitMessage : InitMessageBase
{
public Article Value { get; set; }
public ExampleInitMessage()
{
}
public ExampleInitMessage(
Article value)
{
this.Value = value;
}
}
Sending a Message
Simply create a global instance of the MessageSender and send a message or value:
if (this._articleSender == null)
this._articleSender = new MessageSender<ArticleInitMessage>();
this._articleSender.SendMessage(new
ArticleInitMessage(article));
this._navService.NavigateTo(ViewModelLocator.ArticleUri);
Receiving a Message
Simply create a global instance of MessageReceiver at VM construct time and pass it an action to do:
this._articleReceiver = new MessageReceiver<ArticleInitMessage>((message) =>
{
this.SelectedItem = message.Value;
}, true);
