Programmation en VBA

Report
Introduction to Visual Basic for Applications
programming in Excel
Resources
 FAQ : http://msdn2.microsoft.com/en-us/isv/bb190540.aspx
 Reference : http://msdn2.microsoft.com/en-us/isv/bb190540.aspx
 Books
 Excel online help
Excel programming
 Two ways to access the Excel programming
environment:
 Using the menus
 Alt F11
Development environment
Editor
Project explorer
Property window
Watch
(debug)
Add a function to Excel
Right click on “Microsoft Excel objects” :
Select “Module”
Generalities about VBA
 VBA is compiled on the fly (at the moment of
execution).
 Case insensitive, the VBA editor changes the text case
to agree with syntax of existing objects.
 A function can be called MyFunction but if you type
myfunction the editor will change m and f to upper case.
 Comments are from the ‘ sign to end of line.
 When typing code you may consider using the edit
toolbar.
Structure of a function
Function
delimiters
Argument
listname
Function
Argument
type type
Argument
Function
name
Function body:
Attribution acts like return value
Call from Excel
Requirements for a function to be
called from Excel
 Cannot change the structure of a sheet.
 Cannot change the propeties of a cell.
 If the function calls another function that on should
respect the same restrictions.
 If a function is to be called even if the arguments have
not changed then the Application.Volatile property
should be called.
 Must return a type that Excel knows how to handle.
Subroutines
 Sub’s do not return results unlike functions.
 Sub’s cannot be directely called from Excel as they do
not return results.
 If a Sub is called from a function that is called from
Excel then is should respect the same restrictions as
functions callable from Excel.
Default values
 Function and Sub parameters may be optional. If a
parameter is optional then all following parameters
should also be optional.
Sub ajoutEspace(ByRef str As String, Optional nb As Integer = 5)
 If an
optional
parameter
is
of
type
Variant
then
we
may
Dim prefix
As
String
Sub ajoutEspace(ByRef str As String, Optional vnb As Variant)
testprefix
it’ s=absence
byString
using the Is Missing test.
Space(nb)
Dim
prefix As
str = prefix
strAs Integer
Dim&nb
Debug.Print
str
If IsMissing(vnb)
Then
End Sub nb = 5
Else
nb = CInt(vnb)
End If
prefix = Space(nb)
str = prefix & str
Debug.Print str
End Sub
Named parameters
 Whan calling a functions parameters may be
referenced by their name.
Sub ajoutEspace(ByRef str As String, Optional nb As Integer = 5)
Dim prefix As String
prefix = Space(nb)
str = prefix & str
Debug.Print str
End Sub
ajoutEspace str:=res, nb:=10
Variable declaration
A variable is declared suing the Dim
keyword
Function surfCercle(x As Double) As Double
Dim pi As Double
pi = 3.1415279
surfCercle = x * x * pi
End Function
Variable declaration may be omited. On taht case the
undeclared variables are Variant.
The Option Explicit instruction on top of a module
makes the variable declaration mandatory.
Types
 String : character strings.
 Numerical types: integers, floating point reals (simple




or double precision) and fixed point reals (decimal).
Dates : dates are represented as the number of days
since January 1 1900.
Arays: collections of variables of same type, indexed by
integers. The programmer as the choice of the indexes,
default is 1 to N.
Variant : type that can store data of any other type.
Objets : types that are not part of the language base
types and are defined on libraries.
Strings
 A character string is declared as String as in the
following example
 Dim message As String
 Lots of functions allow string manipulations :
 Len, returns the size
 InStr, looks inside for contents
 Replace, modifies a String
 Etc.
Numerical types
 Integers:
 Byte
 Integer, integer 2 bytes
 Long, integer 4 bytes
 Decimal : Currency
 Floating point reals:
 Single, 4 bytes
 Double, 8 bytes
Booleans and dates
 Boolean, represents a logical condition (true or false).
 Date, represents a date as the number of days since
January 1 1900. There is a one day difference with Java
GregorianCalendar dates.
Arrays
 An array is declared by following the name of a
variable with parentheses and, eventually, a size.
 Elements of an array are accessed
using
Dim t(1 To
10) Asindexes.
Integer
Sub arrTest(j As Integer)
 The global Option
allows to change the starting index
Dim t(1 To 10) As Integer
for arrays, Default
is Integer
1.
Dim i As
i=1
While i <= 10
t(i) = j + I
i=i+1
Wend
End Sub
Function calls
 A function is called by using its name and replacing
the parameter list by a parenthesised list of
expressions of same size.
 A function call may replace any expression of the same
type as the function.
 Exemple :
 X=surfCercle(2.0)+4
Calling a Sub
There are two ways of calling a Sub:
• Call followed by sub name with arguments between()
Function
HelloWorld()
As String
• Nme
of Sub
(without
the keyword Call) folowed by
Dim res Asseparated
String
arguments
byString
, ,
Function HelloWorld() As
res = "Hello World"
Dim
res As String
Call ajoutEspace(res)
res
= "Hello World"
HelloWorld
= res
ajoutEspace
End
Functionres
HelloWorld = res
End
Function
Sub ajoutEspace(ByRef
str As String)
str = " " & str
Sub
str As String)
End ajoutEspace(ByRef
Sub
str = " " & str
End Sub
Sub, Function : parameters
 Two ways to pass a parameter to a function or a Sub:
 By value, the name of the parameter is preceded by the
keyword ByVal.
 By reference the name of the parameter is reseded by the
keyword ByRef. This is the default parameter passing
method.
Global variables
 A variable declared outside a function or Sub body is
global.
 Two types of visibilities are possible:
 Public, visible on all modules,
 Private, visible only on the current module.
Flow control
 Conditionals:
 If Function Signe(x As Double) As Byte
If x > 0 Then
 Iif Function
Signe = 1sPlus(x As Double) As Double
sPlus x=<IIf(x
> 0, x, 0)
ElseIf
0 Then
End
Function
Signe
= -1
Else
Signe = 0
End If
End Function
Loops
 While
 For
 For
Sub arrTest(j As Integer)
Dim t(1 To 10) As Integer
SubDim
arrTest(j
As Integer)
i As Integer
Dimused
t(1 To 10)
As Integer
Each,
with
collections.
Dim
i = 1i As Integer
While i <= 10
Fort(i)
i = =1 To
j + 10
i
t(i)
i ==i j++1 i
Next
i
Wend
End
EndSub
Sub
Cell manipulation
 Sheets and cells in Excel are represented by variables
of type defined on an Excel library, they can be
manipulated directly from VBA.
 A variable exists corresponding to each sheet :
Object usage
 Un object is a variable with a type defined by a class on




an external library.
Like any other variable un object is declared using the
keyword Dim.
Once declared an object is not initialized.
A non initialized object is Nothing.
In order to initialize an object the keyword Set in must
be used in conjunction with the instruction New that
allocates the memory needed by the object.
Objects and classes
 A class is a type that does not belong to the VBA basic
types.
 Classes are defined on libraries.
 A variable whose type is a class is an Object.
 An Objet contains members that may be:
 properties,
 Methods (functions or subs)
 Two objects of same type may have properties with
different values.
Accessing cells
 One of the members of the worksheet class is the
method Cells.
 There are several versions of the method Cells, among
those:
 A version with two integer arguments represnting the
line and column of the cell.
 A version with a single String argument represnting the
cell as in “A1”.
 The Cells method returns an object of type Range that
can be used to manipulate the cell contents.
Range class members
 Value, property, represents the contents of the cell.
 Text, property, represents the text that is displayed on
the cell.
 Formula, property, represents the formula stored on
the cell.
 ClearContents, method, erases the cell contents.
 ClearComments, method, removes the cell comment.
Example
Option Explicit
Sub displaySquare()
Dim i As Integer
For i = 1 To 100
result.Cells(i, 1).Value = i * i
result.Cells(i, 1).Interior.ColorIndex = i Mod 32
Result is an object of type
Next i
Excel.Worksheet
End Sub
Excel -> library
Worksheet -> class
Cells method
Value
from
property
the Worksheet
of the Range
class class
with 2 arguments (there is another
method with same name and 1 argument)
returns an object of type Excel.Range
Events
 Events are special subroutines that are executed
automatically. Event execution is triggered by external
actions..
 Some examples:
 Button click (with mouse or enter key).
Private Sub btnGo_Click()
 Cell contents change
 Cell
displaySquare
Private
Sub
Target As Range)
selection change.
EndWorksheet_Change(ByVal
Sub
If Target.Cells.Count > 1 Or IsEmpty(Target) Then
Exit
Sub
Private Sub
Worksheet_SelectionChange(ByVal
Target As Range)
End 4).Value
If
calc.Cells(2,
= "selection is now " & Target.Address
End Sub
If Target.Address = "$A$1" Then
calc.Cells(1, 4).Value = "A1 Changed"
End If
End Sub
Events
Class name. On
certain cases
Object name
Event name
Errors
 The default behavior of a program when an error
occurs is to stop it and display a message box.
 A different behavior can be specified using the
following instructions:
 On Error Goto 0, restarts the default behavior.
 On Error Resume Next, ignores the errors and moves to
the next instruction.
 On Error Goto <label>, jumps to <label> (line marked
by <label>:) when an error occurs.
 If an error occurs the Err variable is initialized.
Errors (next)
 The Err variable contains several members, the most
important:
 Number, contains the unique error code.
 Description, contains the error description.
 Raise, generates an error (useful to signal an error to
another part of the program).
 Clear, cleans the next error.
Errors(example)
Modifies the
error handling
Sub ajoutEspace(ByRef str As String, Optional vnb As Variant)
Dim prefix As String
Dim nb As Integer
On Error GoTo err_label
If IsMissing(vnb) Then
nb = 5
Else
nb = CInt(vnb)
End If
prefix = Space(nb)
str = prefix & str
Exit Sub
Label
err_label:
MsgBox Err.Description
Error handling End Sub
Class modules
 A class module is useful to define its own classes.
 A class may contain 3 kinds of members:
 Member variables
 Methods
 Properties
 2 different visibilities for members:
 Private
 Public
Creating a class
Example : Share
Option Explicit
Public nom As String
Public cours As Currency
Member variable
Example: share
Option Explicit
Private isCall As Boolean
Public strike As Currency
Public maturity As Date
Public sousjacent As Act
Public Property Let TypeContrat(tp As String)
If LCase(tp) = "call" Then
isCall = True
Else
isCall = False
End If
End Property
Private member
Public members
Property: write
Example: share
Public Property Get TypeContrat() As String
If isCall Then
TypeContrat = "Call"
Else
TypeContrat = "Put"
End If
End Property
Property: read
Example : Stock shares
Public Function GetPrice(r As Double, vol As Double) As Double
Dim td As Date
Dim days2exp As Long
td = Date
days2exp = maturity - td
If isCall Then
GetPrice = Call_Eur(sousjacent.cours, strike, days2exp, r, vol)
Else
GetPrice = Put_Eur(sousjacent.cours, strike, days2exp, r, vol)
End If
End Function
Member function
Class usage
Sub test()
Dim FT As New Act
Dim CallFT As New Opt
Dim price As Double
Declaration/allocation
FT.nom = "Fance Telecom"
FT.cours = 15.3
CallFT.TypeContrat = "Call"
Set CallFT.sousjacent = FT
CallFT.strike = 15
CallFT.maturity = "20/12/2012"
price = CallFT.GetPrice(0.01, 0.2)
Debug.Print price
End Sub
Method usage
Method call
Forms
 Forms are graphical objects that can be displayed on





Excel.
Forms are used to interact with the user.
A form is composed from a canvas to which we add
graphical components.
The Excel toolbox provides different controls (buttons,
text boxes, labels, list boxes, etc.).
Each control provides events that are used to interact
with the user.
To each form a module is associated.
Creating a form
Form and toolbox
Form design
Code of a form
Event for the
click button.
Access to a
property of
another
control

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