VB6 beginners tutorial
- Learn VB6

Advanced VB6 tutorial - Learn Advanced VB6

Systems Analysis - System analysis and Design tutorial for Software Engineering

Browse Topics

- Getting started
- Data Types
- Modules
- Operators in VB6
- VB6 Variable
- VB6 Procedures
- VB6 Control Structures
- Loops in VB6
- VB6 Exit Do & With End With
- Arrays in VB6
- User-Defined Data Types
- VB6 Constants
VB6 Built-in Functions
- Date and Time in VB6
- VB6 Controls
- TextBox Control
- ComboBox & OptionButton
- Label & Frame
- PictureBox & ImageBox
- Timer Control
- ListBox & ComboBox
- VB6 ScrollBar
- Control Arrays in VB6
- Files controls in VB6
- VB6 CheckBox
- Forms in VB6
- Menus in VB6
- MDI Form in VB6
- InputBox
- MessageBox
- Mouse events
- Mouse Move
- Error Handling
Error Handling (2)
VB6 Database

You are here: Visual Basic > VB6 (Beginners Tutorial)

<< Previous | Contents | Next >>

Assigning and returning arrays in Visual Basic 6

Visual Basic 6 adds two important features to arrays. First, you can perform assignments between arrays. Second, you can write procedures that return arrays. You can assign arrays only of the same type and only if the target is a dynamic array. (The latter condition is necessary because Visual Basic might need to resize the target array.)

ReDim a(10, 10) As Integer
Dim b() As Integer
' Fill the a array with data (omitted).
b() = a() ' This works!

It's no surprise that native assignment commands are always faster than the corresponding For…Next loops that copy one item at a time. The actual increment in speed heavily depends on the data type of the arrays and can vary from 20 percent to 10 times faster. A native assignment between arrays also works if the source array is held in a Variant. Under Visual Basic 4 and 5, you could store an array in a Variant, but you couldn't do the opposite—that is, retrieve an array stored in a Variant variable and store it back in an array of a specific type. This flaw has been fixed in Visual Basic 6:

Dim v As Variant, s(100) As String, t() As String
' Fill the s() array (omitted).
v = s() ' Assign to a Variant.
t() = v ' Assign from a Variant to a dynamic string array.

You often use the capacity to assign arrays to build functions that return arrays. Notice that pair of brackets at the end of the first line in the following procedure:

Function InitArray(first As Long, Last As Long) As Long()
ReDim result(first To Last) As Long
Dim i As Long
For i = first To Last
result(i) = i
InitArray = result
End Function

The new capability of returning arrays lets you write highly versatile array routines. Visual Basic 6 itself includes a few new string functions—namely Join, Split, and Filter—that rely on it. (You'll find more about these new string functions in Chapter 5). Here are two examples of what you can do with this intriguing feature:

' Returns a portion of a Long array
' Note: fails if FIRST or LAST are not valid
Function SubArray(arr() As Long, first As Long, last As Long, _
newFirstIndex As Long) As Long()
Dim i As Long
ReDim result(newFirstIndex To last _ first + newFirstIndex) As Long
For i = first To last
result(newFirstIndex + i - first) = arr(i)
SubArray = result
End Function

' Returns an array with all the selected items in a ListBox
Function SelectedListItems(lst As ListBox) As String()
Dim i As Long, j As Long
ReDim result(0 To lst.SelCount) As String
For i = 0 To lst.ListCount - 1
If lst.Selected(i) Then
j = j + 1
result(j) = lst.List(i)
End If
SelectedListItems = result
End Function

More Topics on Visual Basic 6 Arrays

See Also


<< Previous | Contents | Next >>


Home | About Us | Privacy Policy | Contact Us

Copyright © | All Rights Reserved