- Signals & Slots library -
A mechanism for passing messages to otherwise unconnected code elements

A slot is a listener or a transmitter or both, a signal is like a wire.
You connect 2 slots with a signal. A message is send down a signal wire.

In a signal connection, one slot is determined to be the parent or Transmitter
and one the target or listener

When a transmitter slot emits a message it will transmit the message down all
the signal wires that have been registered with it. If a slot is both a listener
and a tranmitter it will re-transmitt any message it receives down all registered signals.

The transmitting and listening slots are never aware of each other. Only the presence
of a signal allows the message to be send.

It is safe to keep telling a slot to send as it'll simply do nothing if no registered
signals are present. In this way you can set up slots in your code that operate in all
conditions making it more flexible to plug and unplug signals whenever you like.

Often the listener slots are sub-classed slots so that a custom handler can be written
for receiving the signal.

The signal class can also be subclassed for the purpose of modifying the message in
transmission before being received by the listener.

The signal can also be set to transmit only once or every time.

The MessageData class is a simple data holder so as to be flexible for a wide
variety of purposes.

Public Class DocumentProcessor



	Public CountUpdate as new Slot()

	

	public Sub ProcessAllDocuments()

		...

		' loop through all documents

		call Me.EmitCountUpdateSignal(count)

		...

	End Sub

	

	Public Function EmitCountUpdateSignal(count As Long)

		Dim msg as new MessageData

		msg.Data("COUNT") = count

		Call Me.CountUpdate.EmitSignal(msg)

	End Function



End Class

Private Class StatusBoxUpdateValue As slot

	Private parent As NotesStatusBox

	Public Sub new(parent As NotesStatusBox), Slot()

		Set Me.parent = parent

	End Sub

	

	Public Function ReceiveSignal(msg As MessageData) As Boolean

		If(Iselement(msg.Data("UPDATE"))) Then



			Call Me.parent.updatevalue(Clng(msg.Data("UPDATE")))

		End If

	End Function

End Class





Public Class NotesStatusBox



	Public UpdateValueSlot as StatusBoxUpdateValue



	Public Sub New ()

		Set Me.updValSlot = New StatusBoxUpdateValue(Me)

	End Sub



	Public Sub updateValue(num as Long)

		...

	End Sub

End Class

Private Class UpdateMeterSignal As Signal

	Public Sub new()

	End Sub



	Public Function GetTargetData(msg As MessageData) As MessageData

		Dim msgNew as new MessageData

		If(Iselement(msg.Data("COUNT))) Then

			call msgNew.AddData("UPDATE", Clng(msg.Data("COUNT")))

		End If

		Set GetTargetData = msgNew

	End Function

End Class

Sub Initialize

	...

	Dim updsig As New UpdateMeterSignal()

	Dim ProgressMeter as new NotesStatusBox()

	Dim DocUpdater as new DocumentProcessor()

	

	

	Call updsig.Connect(DocUpdater.CountUpdate, ProgressMeter.UpdateValueSlot)

	

End Sub