by Rde (54 Submissions)
Category: Data Structures
Difficulty: Beginner
Date Added: Wed 3rd February 2021
Rating: 
(6 Votes)
Array basics for beginners
VBcoders
' There are two areas where arrays can be declared.
' Firstly in the General Declarations section. Arrays declared
' here are seen by all procedures in this form or module:
Private arrayName([intLow To] intHigh) As dataType
' For example:
Private lngArray(2 To 4) As Long
' You can also declare the array as Public, making it visible to
' all forms and modules in the application:
Public arrayName([intLow To] intHigh) As dataType
' For example:
Public strArray(0 To 200) As String
' Secondly, within procedures:
Dim arrayName([intLow To] intHigh) As dataType
' For example:
Dim intArray(0 To 9) As Integer
' You can also specify element size like a string variable:
Dim arrayName([intLow To] intHigh) As dataType * intByteSize
' For example:
Dim strArray(3 To 14) As String * 256
' Also, you can just specify the array length by omitting the
' [intLow To] code shown above. This specifies the upper
' element's index, not neccessarily the arrays length:
Dim ArrayName(intHigh) As dataType
' For example:
Dim intArray(9) As Integer
' This array will be indexed from 0 by default (so the array's
' size will be one greater than intHigh) unless the following
' line is added to the General Declarations section:
Option Base 1
' You can also do this (for single dimensional arrays only):
Dim scores As Variant
scores = Array(81, 49, 80, 71, 92, 66)
' The above scores array will be indexed from 0 unless Option Base 1
' is added to the General Declarations section.
' VB supports static and dynamic arrays. Static arrays are fixed in
' size and can't be changed at runtime, dynamic array sizes can.
' Static arrays are more memory efficient:
Dim array2(10 To 20) As Integer
' Dynamic arrays do not have a size defined when initialized:
Dim array3() As Integer
' You must ReDim a dynamic array to change its size at runtime:
ReDim array3(1 To 4) As Integer
' You can preserve the contents of the array elements when you
' ReDim the array by using the Preserve keyword with ReDim:
ReDim Preserve array3(1 To 9) As Integer
' You can also assign to a dynamic array directly from another
' array without specifying size:
Dim array4() As Integer
array4 = array3
' array4 will now be initialize with the size
' (and element values if any) of array3.
' Visual Basic allows you to use For Each ... Next to enumerate
' the items in an array:
Dim element As Variant
For Each element In array4()
'code to process array elements sequentially
Next
' Because arrays do not have a Count property you can use the
' UBound and LBound methods to establish its length.
' You could use a loop like the following:
For x = LBound(ArrayName()) To UBound(ArrayName())
'code to process array items sequentially
Next
' The arrays empty parentheses are not required, so the first
' line of code above could be like this:
For x = LBound(ArrayName) To UBound(ArrayName)
' To establish the length you could also use the following code
' that subtracts the LowerBound value from the UpperBound value,
' then adds one to the result because the array elements include
' both upper and lower, then returns the result As Integer:
Function GetCount(AnyArray As Variant) As Integer
On Error Resume Next
Dim length As Integer
length = UBound(AnyArray) - LBound(AnyArray) + 1
GetCount = length ' + 1 = inclusive
End Function
' If you know the data type of the array you could declare
' the AnyArray argument as that type instead of As Variant
' to improve performance:
Function GetCount(sngArray() As Single) As Integer
On Error Resume Next