Scripting Dynamic Callbacks
Is this possible?
Wednesday, March 23, 2005 by Dangerousdaze | Discussion: DesktopX
I'm playing around with scripting objects. I have a COM control "myControl" that has a method "subscribe" to create an asynchronous subscriber of messages:
myControl.subscribe "params"
This control actually creates a callback called_newMessage which it fires whenever a new message arrives, so in my case I need to code something like this:
sub myControl_newMessage
[Code to handle the new message]
end sub
I've created this in my script but it doesn't fire. Can you create event handlers on the fly for events from COM objects?
Thanks!
Nick
myControl.subscribe "params"
This control actually creates a callback called
sub myControl_newMessage
[Code to handle the new message]
end sub
I've created this in my script but it doesn't fire. Can you create event handlers on the fly for events from COM objects?
Thanks!
Nick
thomassen
Reply #2 Monday, March 28, 2005 7:10 AM
Reply #2 Monday, March 28, 2005 7:10 AM
Have a look into the WithEvents statement. Not sure if it helps, but it was all I could think of right now.
Dangerousdaze
Reply #3 Monday, March 28, 2005 10:14 AM
Reply #3 Monday, March 28, 2005 10:14 AM
Unfortunately WithEvents is not supported in VBScript. I'm wondering if JScript will help. Either that or I might have to write a plugin which seems like an awful lot of trouble to go to. It just seems a shame - Stardock have given us the ability to embed ActiveX controls but that support is very limited if we cannot consume their events.
Nick
Nick
JavaScout
Reply #4 Tuesday, March 29, 2005 12:42 AM
Reply #4 Tuesday, March 29, 2005 12:42 AM
How are you registering the callback ?
Here is an example of a callback function that works.
The interesting peice is setting the call back function
http.onreadystatechange=GetRef("processMsg")
Hope this helps
Dim http
'Called when the script is executed
Sub Object_OnScriptEnter
getNewMessage()
MsgBox("done on enter")
End Sub
'Called when the script is terminated
Sub Object_OnScriptExit
On Error Resume Next
http.abort
Set http = Null
End Sub
Function getNewMessage()
Set http = createObject("microsoft.xmlhttp")
http.onreadystatechange=GetRef("processMsg")
http.Open "GET","http://www.w3schools.com/xml/note.xml",True
http.Send
End Function
Function processMsg()
If http.readyState=2 Then
MsgBox("http request started")
End If
If http.readyState=4 Then
MsgBox("http response complete")
End If
End Function
Here is an example of a callback function that works.
The interesting peice is setting the call back function
http.onreadystatechange=GetRef("processMsg")
Hope this helps
Dim http
'Called when the script is executed
Sub Object_OnScriptEnter
getNewMessage()
MsgBox("done on enter")
End Sub
'Called when the script is terminated
Sub Object_OnScriptExit
On Error Resume Next
http.abort
Set http = Null
End Sub
Function getNewMessage()
Set http = createObject("microsoft.xmlhttp")
http.onreadystatechange=GetRef("processMsg")
http.Open "GET","http://www.w3schools.com/xml/note.xml",True
http.Send
End Function
Function processMsg()
If http.readyState=2 Then
MsgBox("http request started")
End If
If http.readyState=4 Then
MsgBox("http response complete")
End If
End Function
Dangerousdaze
Reply #5 Saturday, April 2, 2005 8:44 AM
Reply #5 Saturday, April 2, 2005 8:44 AM
Thanks for the reply. Unfortunately the component in question does not supply a property equivalent to onreadystatechange. 
The documentation just states:
# Declare a variable for the listener.
Dim WithEvents myListener as TibrvListener
This declaration triggers VB to automatically define a private subroutine callback stub named myListener_OnMsg. The program must complete this method stub for each listener object.
Nick
The documentation just states:# Declare a variable for the listener.
Dim WithEvents myListener as TibrvListener
This declaration triggers VB to automatically define a private subroutine callback stub named myListener_OnMsg. The program must complete this method stub for each listener object.
Nick
Please login to comment and/or vote for this skin.
Welcome Guest! Please take the time to register with us.
There are many great features available to you once you register, including:
- Richer content, access to many features that are disabled for guests like commenting on the forums and downloading skins.
- Access to a great community, with a massive database of many, many areas of interest.
- Access to contests & subscription offers like exclusive emails.
- It's simple, and FREE!
Reply #1 Sunday, March 27, 2005 6:24 PM
Nick