Solved

the event of the class module

Posted on 1998-08-01
3
267 Views
Last Modified: 2010-05-03
Hi

Can you give me a very simple example to show me how to write an event in a class module?
I know a little bit about that: declare the event in the generea section of the class, raise the event in somewere in some procedures of the class. However where and how to write the code for the event procedure itself?
I also confused what the difference between the event and the function in a class module :-(
0
Comment
Question by:username1
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
3 Comments
 
LVL 2

Accepted Solution

by:
Llandr earned 50 total points
ID: 1467430
Ok. I can see your confusion. The difference between an event and a function is that the function in the class module allows the class itself to perform an action, the event is a call-out, it allows another entity to respond to the function.
Consider this example:

<------ Code start--------->

<Make a class named CTextReader>
Option Explicit

'This class reads text from a file line by line

Public Event LineRead(aLine As String)

Public Sub ProcessFile()
  Dim buffer As String

  Open "c:\Test.txt" For Input As 1
  While Not EOF(1)
    Line Input #1, buffer
    RaiseEvent LineRead(buffer)
  Wend
  Close 1
End Sub
<End of CTextReader>

<Make a Form with one button>

<Form start>
Option Explicit

Public WithEvents aTextReader As CTextReader


Private Sub aTextReader_LineRead(aLine As String)
  MsgBox "Line:" & aLine & " read"
End Sub

Private Sub Command1_Click()
  aTextReader.ProcessFile
End Sub

Private Sub Form_Load()
  Set aTextReader = New CTextReader
End Sub
<Form end>
<--------- Code ends--------->

You see, you say that I will trigger this event and the client chooses how to respond to it (or if to respond at all).
Hope this clarifies it a bit.




0
 

Author Comment

by:username1
ID: 1467431
Hi Llandr

That is a great answer to me, thank you very much.
My understanding is:
1. in a class, declare the event name and put raiseevent in a method.
2. now use the class (say in a form), write the event code and then use the method above to raise it :-)
However, why you use Public instead of DIM or Private in the following line:
Public WithEvents aTextReader As CTextReader

Cheers.

Username1
0
 
LVL 2

Expert Comment

by:Llandr
ID: 1467432
You are correct, I naturally should have written Private (dim works but I don't find it "kosher", better to use private).
Public seems to work also and could be used from the outside.

You have understood points 1 and 2 correctly. :-)
The example is a bit oversimplified but the idea is the same.
Usually you use the raiseevent when you write controls or servers that someone else uses.

Regards:
Llandr
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I’ve seen a number of people looking for examples of how to access web services from VB6.  I’ve been using a test harness I built in VB6 (using many resources I found online) that I use for small projects to work out how to communicate with web serv…
You can of course define an array to hold data that is of a particular type like an array of Strings to hold customer names or an array of Doubles to hold customer sales, but what do you do if you want to coordinate that data? This article describes…
Show developers how to use a criteria form to limit the data that appears on an Access report. It is a common requirement that users can specify the criteria for a report at runtime. The easiest way to accomplish this is using a criteria form that a…
This lesson covers basic error handling code in Microsoft Excel using VBA. This is the first lesson in a 3-part series that uses code to loop through an Excel spreadsheet in VBA and then fix errors, taking advantage of error handling code. This l…

726 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question