How To Return and Assign Arrays with Visual Basic 6.0 (186423)

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:

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