class containing another class

Hi, I'm new to OOP and am having problems creating a class that contains a collection of items from another class. ie I have a LabelTemplate class that represents a label to printed from a Thermal label printer. My LabelTemplate class has a set of properties like label size, labelName,barcode string etc.I also have a class, "PrintFields", that contains properties for a dynamic number of different items to be printed on the label. I want to have this class contain and access a collection of PrintField objects. Any ideas?
Regards
Kev

[548 byte] By [KiwiCoder] at [2007-12-16]

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# 1

There's 2 ways you can do this.

1, is to inherit the class.

Example.
Public Class Drink
Public sub Drink()
End Sub

Public sub Refill()
End sub
End Class

Public class Coffee
Inherits Drink

Public Sugars as Integer
Public Creams as Integer

Public Sub GetCoffee()
Refill()
End sub

Public Sub DrinkCoffee()
Drink()
End sub
End Class
--

The other option, is to make a local variable of the class.

Exmaple.
Public Class Drink
Public sub Drink()
End Sub

Public sub Refill()
End sub
End Class

Public class Coffee
private MyDrink as Drink = New Drink

Public Sugars as Integer
Public Creams as Integer

Public Sub GetCoffee()
MyDrink.Refill()
End sub

Public Sub DrinkCoffee()
MyDrink.Drink()
End sub
End Class

Dustin_H at 2007-9-9 >

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# 2

Hi,
To have a collection of class in your class then try this pseudo-code:
Public Class PrintField
Public fieldValues as String
End Class

Public Class LabelTemplate
Private fieldValues As New Collection

Public Function getfieldValue(index As Integer) As PrintField
Dim retVal As PrintField
retVal = fieldValues(index)
' return the value
End Function

public Sub setFieldValue(f As PrintField)
' Add the new value in the collection
End Sub
End Class
' Also implement the Remove() function

Or you could just simply expose your collection by making it public...
cheers,
Paul June A. Domag

PaulDomag at 2007-9-9 >

# 3

Thanks Paul, I just aboutr have it, I think?.
The problem is Button3 click causes an error.Would you mind helping, I guess the answer must be obvious but I can't see it.
Public Class PrintField
Private xposValue As Integer
Public Property xpos() As Integer
Get
Return xposValue
End Get
Set(ByVal value As Integer)
xposValue = value
End Set
End Property
Private yposValue As Integer
Public Property ypos() As Integer
Get
Return yposValue
End Get
Set(ByVal value As Integer)
yposValue = value
End Set
End Property
End Class
Public Class LabelTemplate
Private PrintFields As New Collection
Public Function getfldValue(ByVal index As Integer) As PrintField
Dim retVal As PrintField
retVal = CType(PrintFields(index), PrintField)
' return the value
End Function
Public Sub setFldValue(ByVal f As PrintField)
PrintFields.Add(f)
End Sub
Private FieldcountValue As Integer
Public ReadOnly Property Fieldcount() As Integer
Get
FieldcountValue = PrintFields.Count
Return FieldcountValue
End Get
End Property
End Class

Public Class Form3
Private anitem As New PrintField
Private nextitem As New PrintField
Private mylabel As New LabelTemplate
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
anitem.xpos = 1111
anitem.ypos = 2222
mylabel.setFldValue(anitem)
nextitem.xpos = 3333
nextitem.ypos = 4444
mylabel.setFldValue(nextitem)
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
MsgBox(mylabel.getfldValue(0).xpos.ToString)
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
'This causes an error
MsgBox(mylabel.getfldValue(1).ypos.ToString)
End Sub
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
MsgBox(mylabel.Fieldcount.ToString) 'This works
End Sub
End Class

KiwiCoder at 2007-9-9 >

# 4

Hi,
In your getFldValue() function, what I meant by return the value was declaring Return retVal coz at that time I was not sure on the return keyword in VB...
cheers,
Paul June A. Domag

PaulDomag at 2007-9-9 >

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