Quick Question, Please Help!

[winapi]

HI,
I have been programming in visual basic for about 2yrs. I am all self taught and I have never used the class module before. I know that a regular module can be used to declare global sub/funtion/vars/api declares, but what exactly does the class module do and what are the major differences. Thanks

Edited by winapi on 03-12-2000 at 07:20 PM

[Sam Finch]

Class Modules are completly Different to modules.
I have to stress this Because I got the 2 Confused for a while, although for some reason I knew about class modules before modules. (Probably someting to do with my boss being a class module fanatic)

Basicly a class module is used to store and manipulate data in one object.

They have properties, methods and events much like user controls but you cant use them at design time and you cant put them on a form or see them.

I'm a bit stuck for simple examples
but say you're programming a **** roleplaying type game and you want to keep track of a characters Money health etc
(Please don't think i devote any of my time to roleplaying games of any sort but this is the only example I can think of that uses most of a class modules capabilities)

you could have a class module representing a character.

This is a quick example with

Properties:

Name as string
Money as long
Health as byte 'From 0 to 100, 0 means he's dead

Methods:

Hurt(Amount as byte, Randomize as boolean)
'Takes away a characters health if randomize is selected it 'picks a random amount to take away from 0 to Amount

Cure(amount as byte, Randomize as byte)
'Similar to Hurt but adds to a characters healh instead
'of taking it away

Events:

Dies Character is dead

The Code Would Be as Follows

Option Explicit

Dim propMoney As Long
Dim propHealth As Byte
Dim propName As String


Event Dies()


Public Property Let Money(Data As Long)
If Not Data < 0 Then propMoney = Data
End Property


Public Property Get Money() As Long
Money = propMoney
End Property



Public Property Let Health(Data As Byte)
propHealth = Data
End Property


Public Property Get Health() As Byte
If Data > 0 And (Not Data > 100) Then Health = propHealth
End Property



Public Property Let Name(Data As String)
propName = Data
End Property


Public Property Get Name() As String
Name = propName
End Property


Public Sub Hurt(Amount As Byte, Randomize As Boolean)

Dim intNewHealth As Integer 'Integer in case health is negative

If Randomize Then

    intNewHealth = propHealth - Fix(Rnd * (Amount + 1))

Else

    intNewHealth = propHealth - Amount

End If

If Not intNewHealth > 0 Then

    propHealth = 0

    RaiseEvent Dies
    
Else

    propHealth = intNewHealth
    
End If

End Sub


Public Sub Cure(Amount As Byte, Randomize As Boolean)

Dim intNewHealth As Integer 'I just copied the hurt code and changed some signs so we'll still use the integer

If Randomize Then

    intNewHealth = propHealth + Fix(Rnd * (Amount + 1))

Else

    intNewHealth = propHealth + Amount

End If

If intNewHealth > 100 Then

    propHealth = 100
    
Else

    propHealth = intNewHealth
    
End If

End Sub

Private Sub Class_Initialize()

propName = ""
propMoney = 0
PropHealth = 100

End Sub

you only need to do the code once and you have a variable which represents a character and handles all the code needed for him which keeps the code out of your standard modules and keeps everything nice and readable

you can have more than one instance of a class running at the same time with different property values for each

declare them with

Dim objDaveTheFictionalCharacter as New clsCharacter
'ClsCharacter is what you called your class

and get rid of them with

Set objDaveTheFictionalCharacter = Nothing

You can pass these to Procedures, Return them from functions Stick them in collections and everything as long as you remember

1 classes need to be initialized either by declaring them as
Dim objWhatever as new clsWhatever

or by using
Set objWhatever = New clsWhatever

2.
Copy a class to a new variable with

Set objWhatever2 = objWhatever

3.
Whenever you pass classes to procedures or put them in new variables they are passed by reference so both variables access the same data so if you change a property in one dont expect it to be the same in the other (This can be veryfrustrating or you can use it to your advantage, Your choice)

3,. Terminate a class with
set objWhatever = Nothing

4. If you have 2 variables pointing to the same instance of a class and you set one to nothing the object will still be running and you can still access it from the other variable, it's only when all references to that instance terminates.

Hope his Helps

[jcouture100]

The difference between a regular every day module
and a class module can be summed up this way:

A regular module can have Subs and Functions that you
call in your application. You're familiar with this
type so I won't say much else about this.

A class module also has Subs and Functions as well as
Property Let and Property Get declarations. The Subs
and Functions of a Class Module become the Events and
Methods of the Class. IE. The Click event of a button
class or the AddItem Method of a ComboBox Class.

The Property Let and Property Get parts become the
Properties of the class. IE. On a label control, you can
set the Caption Property to anything you want using the
Label1.Caption = "Hi There". This is actually using the
Property Let of the Label Class to set this value for the
Caption Property.

By using a class module, you're just building your own
class of objects where you get to choose which properties,
events and methods you want to make available to the
application via your Subs, Functions, and Property Let/Get.


Hope this helped.