Who's afraid of classes?

Ok, this may seem to a lot of you like a stupid question, and I don't blame you.

I've been programming in VB for about 4 years now (about 1 year was for fun only) and I've never used classes in any of my projects (except DLLs). I used everything but classes. I don't have anything against them, and I'm not afraid of them :) , I just don't understand what's so special about them. When and why do I use them?

Can anyone answer this question please?
I see everybody use classes and they seem very useful, I just don't know how/when to use them.

BTW: Please don't flame me about this.

:( Anyone?

The most obvious reason I can think of for using Classes is when you have a database type project. I would set up a class for each table. Each class represents a table object, each property of the class represents a field.

Ok it's very basic but it's as good a start as any.

How can you make it so every property of the class is a field?

If you've a table with:

Name
Age
Tel No.
Email Addresss

you'd have property let/gets for each of those within a class. The class maybe something like 'clsPerson' and you may then have a class which hold a collection of these classes called 'clsPersons'.

Having a class represent a table on a DB is all very well but it does require you to have a good, normalised, structure to your DB.

In the main classes are pretty handy but I've come across some which use, gulp!, Global variables. If you come across a class using a global you are entitled to shoot the author.......but only in Uzbekistan where they've just passed a law allowing this. Oh in Wales you are permitted to batter the author into unconsciousness with a small sheep.

Good, I knew my herd will come in handy :p

Classes allow you to share code easily among multiple projects (assuming their compiled into COM objects).

If you encapsulate your business logic into the classes it then easy to update the applications that you the objects without recompiling them.

Just my 2 cents

:) :) :)

Classes let you incorporate 'basic' OOP (Object Orientated Programming) technicues into your program in VB. In my opinion, they let you structure your programs more efficiently than other ways that exist.

Bye

Classes are great when you get into complex things such as games. For example, in a game, you would need to create a player. A player can Jump, Attack, Defend, Run etc. There are also things that describe the character such as Hitpoint, Strength, Defence, Speed etc.

All of this can be organized into a class, for example:

Code:

---

'local variable(s) to hold property value(s)
Private mvarHitpoints As Byte
Private mvarStrength As Integer
Private mvarDefence As Integer
Private mvarSpeed As Integer
Public Sub Attack()
    'Attack someone
End Sub

Public Sub Jump(Height As Byte)
    'Jump
End Sub

Public Sub Run(Speed As Integer)
    'Run
End Sub

Public Property Let Speed(ByVal vData As Integer)
    mvarSpeed = vData
End Property

Public Property Get Speed() As Integer
    Speed = mvarSpeed
End Property

Public Property Let Defence(ByVal vData As Integer)
    mvarDefence = vData
End Property

Public Property Get Defence() As Integer
    Defence = mvarDefence
End Property

Public Property Let Strength(ByVal vData As Integer)
    mvarStrength = vData
End Property

Public Property Get Strength() As Integer
    Strength = mvarStrength
End Property

Public Property Let Hitpoints(ByVal vData As Byte)
    mvarHitpoints = vData
End Property

Public Property Get Hitpoints() As Byte
    Hitpoints = mvarHitpoints
End Property

---

Now we can use that class to create a player

Code:

---

'Create a player
Dim Player1 As CPlayer
Set Player1 = New CPlayer
   
Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)

    If KeyCode = vbKeyUp Then
        'Jump at (at a height of 15 units) when the UP key is pressed
        Player1.Jump (15)
    End If
   
End Sub

Private Sub Form_Load()

    'Set the properties of the character
    With Player1
        .Hitpoints = 25
        .Strength = 20
        .Speed = 10
        .Defence = 10
    End With
   
End Sub

---

Remember, since we have a 'template' of a Player, we can create as many as we want.

Code:

---

Dim Player1 As CPlayer
Dim Player2 As CPlayer
Dim Player3 As CPlayer
Dim Player4 As CPlayer

'...

Dim Player100 As CPlayer

---

It's much easier (and faster) to create a class for a player than to create 700 different variabes/functions for each player!

Thanks guys :)

And let's say I have a DB project which is not very complex (One connection, and about four recordsets that don't have anything to do with each other), will a class be useful here?

Hold on, so from what I see, a class is sort of like a a UserControl just without the GUI. Right?

You have the right idea, but remember; a UserControl is a type of class too, so following sentence would make more sense.

A UserControl is a class with a GUI.

Thanks :D