Q186423: HOWTO: Return and Assign Arrays with Visual Basic 6.0

Article: Q186423
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 6.0 
- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
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SUMMARY
=======

New to Visual Basic 6.0 is the ability to assign an array or return an array
from a function. This article demonstrates these new features.

MORE INFORMATION
================

One of the benefits of assigning arrays is that the compiler will type- check
the assignments the same way it does for other variable assignments. Also you
can trap for a Type Mismatch error if you are returning an array from a
late-bound object.

When making array assignments, the array on the left side of the argument must me
a dynamic array. Otherwise, you will receive the following compiler error:

  "Can't assign to array"

This is the same compiler error you will get if you try to assign arrays of
different types. For example, you will receive this error if you attempt to
assign an Integer array to a String array:

     StringArray = IntegerArray

Step-by-Step Example
--------------------

1. Start a new Standard EXE project. Form1 is created by default.

2. Add a Class Module to the project.

3. Place the following code in the Class Module:

        Option Explicit

        Public Function ArrayFromClass() As String()
           Dim aStr(1 To 10) As String
           Dim i As Integer
           For i = 1 To 10
              aStr(i) = "Class array element " & Str(i)
           Next i
           ArrayFromClass = aStr()
        End Function

4. Place three CommandButtons on form1.

5. Add the following code to form1:

        Option Explicit

        Private aiLeftSide() As Integer
        Private asLeftSide() As String
        Private aiRightSide(1 To 10) As Integer
        Private asRightSide(1 To 10) As String
        Private obj As Object

        Private Sub Command1_Click()
           Dim i As Integer
           aiLeftSide = aiRightSide
           'try assigning arrays of different types by changing the next line
           ' to aiLeftSide = asRightSide
           asLeftSide = asRightSide
           For i = 1 To UBound(aiLeftSide)
              Debug.Print aiLeftSide(i)
           Next i
           For i = 1 To UBound(asLeftSide)
              Debug.Print asLeftSide(i)
           Next i
        End Sub

        Private Sub Command2_Click()
           Dim i As Integer
           Dim aInt() As Integer
           Dim astr() As String
           aInt = ReturnIntArray
           'try assigning arrays of different types by changing the next line
           ' to aInt = ReturnStringArray
           astr = ReturnStringArray
           For i = 1 To UBound(aInt)
              Debug.Print aInt(i)
           Next i
           For i = 1 To UBound(astr)
              Debug.Print astr(i)
           Next i
        End Sub

        Private Sub Command3_Click()
           'To see what kind of error you get when a late-bound object
           'returns an array that is of a different type than the receiving
           'array, change the next line of code to be Dim astr() as Integer
           Dim astr() As String
           Dim i As Integer
           astr = obj.ArrayFromClass
           For i = 1 To UBound(astr)
              Debug.Print astr(i)
           Next i
        End Sub

        Private Sub Form_Load()
           Dim i As Integer
           Command1.Caption = "Assign Array"
           Command2.Caption = "Call Function that returns Array"
           Command3.Caption = "Call Object method that returns Array"
           For i = 1 To 10
              aiRightSide(i) = i
              asRightSide(i) = "This is element " & Str(i)
           Next i
           Set obj = New Class1
        End Sub

        Private Function ReturnStringArray() As String()
           Dim aString(1 To 10) As String
           Dim i As Integer
           For i = 1 To UBound(aString)
              aString(i) = "Element " & Str(i)
           Next i
           ReturnStringArray = aString()
        End Sub

        Private Function ReturnIntArray() As Integer()
           Dim aInt(1 To 10) As Integer
           Dim i As Integer
           For i = 1 To 10 'UBound(aInt)
              aInt(i) = i
           Next i
           ReturnIntArray = aInt()
        End Sub

6. Run the form and click on the different command buttons. You will see the
  results in the Immediate Window.

(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Brian
Combs, Microsoft Corporation


Additional query words: kbDSupport kbDSD kbVBA kbVB600 kbDSupport

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Keywords          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVBA600 kbVB600
Version           : WINDOWS:6.0
Issue type        : kbhowto

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