Putting Excel Tables into a Custom Class - vba

Question

I'm new to using VBA classes, and I think what I want to do -- using them with ListObjects -- is more of an "intermediate" than "beginner" technique.
Let's say I have two tables related to cars.
tblCarDesc
ID MAKE MODEL DOORS ENGINE
1 Chevrolet Corvette 2 V8
2 Ford Escort 4 V6
3 Rolls-Royce SilverCloud 4 V8
tblCarProd
ID COUNTRY TYPE
1 US Sport
2 US Economy
3 UK Luxury
(The same cars are in both tables, and shown by the ID numbers.)
I want to have a class called objCars that includes the fields (columns) from both tables. That way, when referring to Car #3, objCars.Make would be "Rolls-Royce" and objCars.Type would be "Luxury".
1) Is there a way to import both tables into objCars?
Perhaps I would create an array big enough to hold all the columns, then load both tables into it. The tutorial I've been reading says that I would then create a Collection, loop through each row of the array, make a new instance of objCars, and assign objCars.Make, objCars.Model, etc., for each row. Then each item of the Collection would contain a car. (Or something like that. I don't really know much about Collections either.) If that's right, is it the best way?
2) How exactly does one refer to a specific car? The examples I've read like to loop through Collections and work on each item therein, but what if I want to extract a particular item? I know the Ford is Car #2; how do I get the objCars.Make and objCars.Model for that particular ID number?

Answer 1

I would have two classes. A class clsCar for one car and a class clsCars for a collection of cars.
Each of this classes may have setter and getter methods and also may have custom methods if needed. Especially the clsCars should have a set of getBy...-methods to get a car or a collection of cars from the collection by criterion.
Example:
clsCar:
Private pID As Long
Private pMAKE As String
Private pMODEL As String
Private pDOORS As Integer
Private pENGINE As String
Private pCOUNTRY As String
Private pTYPE As String
Public Property Get ID() As Long
ID = pID
End Property
Public Property Let ID(Value As Long)
pID = Value
End Property
Public Property Get MAKE() As String
MAKE = pMAKE
End Property
Public Property Let MAKE(Value As String)
pMAKE = Value
End Property
Public Property Get MODEL() As String
MODEL = pMODEL
End Property
Public Property Let MODEL(Value As String)
pMODEL = Value
End Property
Public Property Get DOORS() As Integer
DOORS = pDOORS
End Property
Public Property Let DOORS(Value As Integer)
pDOORS = Value
End Property
Public Property Get ENGINE() As String
ENGINE = pENGINE
End Property
Public Property Let ENGINE(Value As String)
pENGINE = Value
End Property
Public Property Get COUNTRY() As String
COUNTRY = pCOUNTRY
End Property
Public Property Let COUNTRY(Value As String)
pCOUNTRY = Value
End Property
Public Property Get CarTYPE() As String
CarTYPE = pTYPE
End Property
Public Property Let CarTYPE(Value As String)
pTYPE = Value
End Property
Public Function toString() As String
toString = pID & "; " & _
pMAKE & "; " & _
pMODEL & "; " & _
pDOORS & "; " & _
pENGINE & "; " & _
pCOUNTRY & "; " & _
pTYPE
End Function
clsCars:
Private pCars As collection
Private Sub Class_Initialize()
Set pCars = New collection
End Sub
Public Sub add(oCar As clsCar)
pCars.add oCar
End Sub
Public Function getByIndex(lIndex As Long) As clsCar
Set getByIndex = pCars.Item(lIndex)
End Function
Public Function getByID(lID As Long) As clsCar
Dim oCar As clsCar
For Each oCar In pCars
If oCar.ID = lID Then
Set getByID = oCar
End If
Next
End Function
Public Function getByEngine(sEngine As String) As collection
Dim oCar As clsCar
Set getByEngine = New collection
For Each oCar In pCars
If oCar.ENGINE = sEngine Then
getByEngine.add oCar
End If
Next
End Function
default Module:
Public oCars As clsCars
Sub initialize()
Dim oCar As clsCar
Dim oListObject As ListObject
Dim oListRow As ListRow
Dim oCells As Range
Set oCars = New clsCars
Set oListObject = Worksheets("Sheet1").ListObjects("tblCarDesc")
For Each oListRow In oListObject.ListRows
Set oCells = oListRow.Range.Cells
Set oCar = New clsCar
oCar.ID = oCells(, 1).Value
oCar.MAKE = oCells(, 2).Value
oCar.MODEL = oCells(, 3).Value
oCar.DOORS = oCells(, 4).Value
oCar.ENGINE = oCells(, 5).Value
oCars.add oCar
Next
Set oListObject = Worksheets("Sheet1").ListObjects("tblCarProd")
Dim lID As Long
For Each oListRow In oListObject.ListRows
Set oCells = oListRow.Range.Cells
lID = oCells(, 1).Value
Set oCar = oCars.getByID(lID)
If Not oCar Is Nothing Then
oCar.COUNTRY = oCells(, 2).Value
oCar.CarTYPE = oCells(, 3).Value
End If
Next
MsgBox oCars.getByIndex(2).toString
For Each oCar In oCars.getByEngine("V8")
MsgBox oCar.toString
Next
End Sub

Answer 2

I would use a class for each, and an array of each also, so arrCars holds clsCars, and arrProd holds clsProduction. I would then use the index of each for each array when populating, so arrCars(1)=Corvette and arrProd(1)=US Sport then from each you can refer to the others, so if x=3, cars(x) and prod(x) will be correct. Or use a vlookup in excel first, and make one larger table, with the need for only 1 ID then, if that is the way they are related, but can a Bentley also be 3. Its not quite clear what you mean by the 2nd table, is there an entry for each car, or is it like catgeorising the car further, just using a certain selection. Another idea would be to have an extra property in the car class, of ProductionID and then use a static production "table" of classes to refer to.