Class Object containing an array of other objects-CodePudding

I've programmed in several languages but i'm at my first tests on VBA.

I need to make a class who has as a property, an array of objects of another class. Let's make an example a Person class who keeps info about name, surname and addresses. And an address class who keeps info about a street and zipcode. A person could have many addresses so Person should have an arrays of Addresses.

class Address
Private pStreet as String
Private pZip as Int

Public Property Let Street(val As String)
    pStreet = val
End Property
Public Property Get Street() As String
    Street = pStreet
End Property
Public Property Let Zip(val As String)
    pZip = val
End Property
Public Property Get Zip() As String
    Zip = pZip
End Property

class Person
Private pName as String
Private pSurname as String
Private pAddresses() as Address

Public Property Let Name(val As String)
    pName = val
End Property
Public Property Get Name() As String
    Name = pName
End Property

Public Property Let Surname(val As String)
    pSurname = val
End Property
Public Property Get Surname() As String
    Surame = pSurname
End Property

How should i manage the array of Address?

i tried with such code but if i try to call this method on a person object i get an error" obect doesn't support this property or method"

Public Sub addAddress(val as Address)
    ReDim pAddresses(1)
    pAddresses(0) = val
End Sub

what's the way to do this? i cannot find any tutorial or something who shows how to use arrays of objects inside of an object

CodePudding user response：

When you use redim, it actually makes a brand new array of the specified size, so all existing data is lost. To copy the values from the old array to the new one, you need the 'Preserve' keyword as follows

ReDim Preserve pAddresses(1)

But this is really inefficient as adding another element to the array requires rewriting the entire array. You are probably better of using a collecion. So instead of declaring pAddress like this

Private pAddresses() as Address  ' delcare as an array

do it like this

Private pAddresses as New Collection ' declare as a collection

Now your method to add an address can look like this:

Public Sub addAddress(val as Address)
    pAddresses.Add val
End Sub

The indices for collections start counting at one instead of zero (as arrays do) so the following line prints the first entry in the collection

Debug.Print pAddresses(1)

CodePudding user response：

Change your code to this should work

   Public Sub main()

    Dim val As New Address
    val.Street = "MyStreet"
    val.Zip = 666
    Dim val2 As New Address
    val2.Street = "my New Street"
    val2.Zip = 999
    
    
    Dim myself As New Person
    With myself
        .Name = "its Me"
        .Surname = "Smith"
        Call .addAddress(val)
        Call .addAddress(val2)
    End With

   End Sub
    
    
    
        
     class Address
        Private pStreet As String
        Private pZip As Integer
        
        Public Property Let Street(val As String)
            pStreet = val
        End Property
        Public Property Get Street() As String
            Street = pStreet
        End Property
        Public Property Let Zip(val As String)
            pZip = val
        End Property
        Public Property Get Zip() As String
            Zip = pZip
        End Property
        
     end class
    
    
     
        
    class person
            
    Private pName As String
    Private pSurname As String
    Private pAddresses As Collection
    
    Private Sub Class_Initialize()
        Set pAddresses = New Collection
    End Sub
    
    Public Property Let Name(val As String)
        pName = val
    End Property
    Public Property Get Name() As String
        Name = pName
    End Property
    
    Public Property Let Surname(val As String)
        pSurname = val
    End Property
    Public Property Get Surname() As String
        Surame = pSurname
    End Property
    
    Public Sub addAddress(val As Address)
        Call pAddresses.Add(val)
    End Sub
            
    end class

First, create objects using NEW Keyword and then SET the objects to variables. You Always have to use the SET Keyword if you want to store a reference to an existing object inside of an variable.

But the better way would be to use a collection instead of an array.

Nice Starting Point Excel Collection Ultimate Guide