VBA - Returning array from Property Get

ThomasMcLeod picture ThomasMcLeod · Apr 10, 2011 · Viewed 29k times · Source

If arrays are returned by reference, why doesn't the following work:

'Class1 class module
Private v() As Double
Public Property Get Vec() As Double()
    Vec = v()
End Property
Private Sub Class_Initialize()
    ReDim v(0 To 3)
End Sub
' end class module

Sub Test1()
    Dim c As Class1
    Set c = New Class1
    Debug.Print c.Vec()(1) ' prints 0 as expected
    c.Vec()(1) = 5.6
    Debug.Print c.Vec()(1) ' still prints 0
End Sub

Answer

Clayton S picture Clayton S · May 31, 2013

You don't have a let property. Also, the get property is returning the entire array, rather than just the element in question. Change the return type of Property Get from Double() to just plain Double. Add Property Let. Note that it takes two inputs, but only one is passed to it. The last variable (MyValue, in this case) is assumed to get it's value from whatever is after the = sign. Put a break point somewhere early in Test1() and see how the values are affected in the Locals window. Compare the variables created by the original code versus my code:

'Class1 class module
Private v() As Double
Public Property Get Vec(index As Long) As Double
    Vec = v(index)
End Property
Public Property Let Vec(index As Long, MyValue As Double)
    v(index) = MyValue
End Property
Private Sub Class_Initialize()
    ReDim v(0 To 3)
End Sub
' end class module

'Begin module
Sub Test1()
    Dim c As Class1
    Set c = New Class1
    Debug.Print c.Vec(1) ' prints 0 as expected
    c.Vec(1) = 5.6
    Debug.Print c.Vec(1) ' prints 5.6
End Sub
'End module