README.md
December 4, 2022 · View on GitHub
Description
Array basics for beginners
More Info
| Submitted On | |
| By | Rde |
| Level | Beginner |
| User Rating | 4.7 (28 globes from 6 users) |
| Compatibility | VB 4.0 (32-bit), VB 5.0, VB 6.0 |
| Category | Data Structures |
| World | Visual Basic |
| Archive File |
Source Code
' 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
Dim length As Integer
length = UBound(sngArray) - LBound(sngArray) + 1
GetCount = length ' + 1 = inclusive
End Function
' Calling the function is as easy as:
intCount = GetCount(myArray())
' Multi-dimensional arrays
' Each dimension of the array must contain the same data type.
' The second-last and last dimensions of a multi-dimensional array
' are normally considered to be a Row and a Column respectively.
Private multiArray(1 To 5, 1 To 3) As Integer
' So for a two dimensional array in VB the dimension (row) is
' defined first, and the number of elements (cols) for each
' dimension defined second:
Public 2DArray(1 To 2, 1 To 8) As Long
' This array is a two dimensional array containing 8 elements
' in each dimension:
Dim i1 As Integer, i2 As Integer
For i1 = 1 To 2
For i2 = 1 To 8
2DArray(i1, i2) = "Cell " & CStr(i1) & "," & CStr(i2)
Next
Next
' You can also assign arrays to the elements of other arrays to
' create multi-dimensional arrays:
Public Sub CreateMultiArray()
Dim intX As Integer ' Declare counter variable
' Declare and populate an integer array
Dim countersA(1 To 4) As Integer
For intX = 1 To 4
countersA(intX) = intX
Next intX
' Declare and populate a string array
Dim countersB(1 To 4) As String
For intX = 1 To 4
countersB(intX) = "hello"
Next intX
' Declare a new two-member array
Dim arrX(1 To 2) As Variant
' Populate the array with other arrays
arrX(1) = countersA()
arrX(2) = countersB()
' Display a member of each array
MsgBox arrX(1)(2)
MsgBox arrX(2)(3)
End Sub
' To increase the size of an array without losing its current
' values use the Preserve keyword:
ReDim Preserve DynArray(UBound(DynArray) + 1)
' Only the upper bound of the last dimension in a multi-dimensional
' array can be changed when you use the Preserve keyword; if you
' change any of the other dimensions, or the lower bound of the
' last dimension, a run-time error occurs.
' Thus, you can use code like this:
ReDim Preserve Matrix(10, UBound(Matrix, 2) + 1)
' But you cannot use this code:
ReDim Preserve Matrix(UBound(Matrix, 1) + 1, 10)
' Multi-dimensional array demonstration
' The following code can be copied and pasted into the form of
' a new project and after creating three command buttons named
' cmdFill, cmdShow and cmdMulti you can run the program:
Option Explicit
Option Base 1
Private multiArray(1 To 5, 1 To 3) As String
Private counter As Integer
Private Sub cmdFill_Click()
Dim idx1 As Integer, idx2 As Integer
For idx1 = 1 To 5
For idx2 = 1 To 3
counter = counter + 1
multiArray(idx1, idx2) = "Cell " & CStr(counter)
Next
Next
End Sub
Private Sub cmdShow_Click()
Me.Refresh
CurrentY = 100
Print " Dim multiarray(1 To 5, 1 To 3) As String"
CurrentY = 400
Dim idx1 As Integer, idx2 As Integer
For idx1 = 1 To 5
For idx2 = 1 To 3
Print " multiarray(" & _
CStr(idx1) & "," & CStr(idx2) & ") = " & _
Chr(34) & multiArray(idx1, idx2) & Chr(34)
Next
Next
End Sub
Private Sub cmdMulti_Click()
Dim intX As Integer ' Declare counter variable
' Declare and populate an integer array
Dim countersA(4) As Integer
For intX = 1 To 4
countersA(intX) = intX
Next intX
' Declare and populate a string array
Dim countersB(4) As String
For intX = 1 To 4
countersB(intX) = "hello"
Next intX
' Declare a new two-member array
Dim arrX(1 To 2) As Variant
' Populate the array with other arrays
arrX(1) = countersA()
arrX(2) = countersB()
' Display a member of each array
MsgBox arrX(1)(2)
MsgBox arrX(2)(3)
End Sub