Beginner to User Defined Data Types (Custom Type, UDTs)

Disadvantage 1. UDT can be public just like any other variable. You just need to scope them in the correct place.

Public Type Car
    Make    As String
    Model   As String
    Price   As Currency
    Km      As Long
End Type

Public g_udtMyCar As Car

Sub Example3()
    'use UDTs (defined at top of module)
    'e.g.
    g_udtMyCar.Make = "Unknown"

' do something
End Sub

Disadvantage 2. Again depends on your scope definition

Disadvantage 3. Incorrect, you can redim and redim preserve

Option Explicit

Public Type Car
    Make    As String
    Model   As String
    Price   As Currency
    Km      As Long
End Type

Public g_udtMyCars() As Car
Sub Example4()
    
    ReDim g_udtMyCars(1 To 3)
    
    g_udtMyCars(1).Make = "Ford"
    g_udtMyCars(2).Make = "Audi"
    g_udtMyCars(3).Make = "BMW"
    
End Sub
Sub Example5()
    
    ReDim Preserve g_udtMyCars(1 To 5)
    
    g_udtMyCars(4).Make = "Mercedes"
    g_udtMyCars(5).Make = "VW"
    
End Sub
Sub Test()
    
    Dim lngIndex As Long
    
    Example4
    Example5
    
    For lngIndex = LBound(g_udtMyCars) To UBound(g_udtMyCars)
        Debug.Print lngIndex, g_udtMyCars(lngIndex).Make
    Next
    
End Sub

Disadvantage 4. I don't see the use of udt against normal variables having a performance hit. Do you have any evidence of this?

Disadvantage 5. Don't see why, you need to clarify your statement about why they are hard to use in addin.

Disadvantage 6. No they are not.

extends previous code example.

Sub Test()
    
    Dim lngIndex As Long
    
    Example4
    Example5
    
    For lngIndex = LBound(g_udtMyCars) To UBound(g_udtMyCars)
        Debug.Print lngIndex, g_udtMyCars(lngIndex).Make
    Next
    
    Example6 g_udtMyCars(2)
    Example7 g_udtMyCars
    
    Debug.Print GetCar(g_udtMyCars, "Ford").Price
    
End Sub
Sub Example6(MyCar As Car)
    Debug.Print MyCar.Make
End Sub


Sub Example7(Cars() As Car)

    Dim lngIndex As Long
    
    For lngIndex = LBound(Cars) To UBound(Cars)
        Cars(lngIndex).Price = Int((50000 - 15000 + 1) * Rnd + 15000)
Debug.Print Cars(lngIndex).Make, Cars(lngIndex).Price
    Next

End Sub
Function GetCar(Cars() As Car, Name As String) As Car
    Dim lngIndex As Long
    
    For lngIndex = LBound(Cars) To UBound(Cars)
        If StrComp(Cars(lngIndex).Make, Name, vbTextCompare) = 0 Then
            GetCar = Cars(lngIndex)
            Exit Function
        End If
    Next
End Function

Disadvantage 7. no more than stanadard variables

Originally Posted by Andy Pope

...

Appreciate your detailed myth busting of UDTs disadvantages. +1
At this rate, I may end up using them after all!

1. (Tests code provided). :eep: Whoa. It's now working! Now why didn't it work in my current project? Will go back, test and report back.
2. As above
3. (dazed) That's incredible. Then what did Chip Pearson mean? See: http://www.cpearson.com/excel/classes.aspx (1/3 down the page - where he describes 3 disadvantages to Type)
4. I was reading about UDTs having a slight impact on code performance. It involved a test that used LenB in Immediate window to measure the size of variables. But I can't remember where I read it and a quick google can't find it again
5. This? http://stackoverflow.com/questions/1...-from-an-addin
6. I have come across a few web pages re UDTs and arrays. Here's one: http://www.vbaexpress.com/forum/show...r-Defined-Type
7. I concur.

UPDATE: 1 & 2 tested in current project. Working fine now. (No idea why it played up previously)