Advanced VBA Techniques. Alison Balter InfoTech Services Group

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1 Advanced VBA Techniques Alison Balter InfoTech Services Group

KeyStone Learning Systems, SAMS Publishing and Experts Exchange Microsoft Access MVP

2 About Me Started InfoTech Services Group in 1990 Wrote first book for SAMS on Access 2.0 Have written 15 books on Access and SQL Server Have authored over 300 videos for KeyStone Learning Systems, SAMS Publishing and Experts Exchange Microsoft Access MVP Expert for Experts Exchange Husband Dan is business partner Children Alexis, 17, and Brendan, 14

3 About Me Spend 90% of my time developing custom access applications 90% of applications that I design are client/server Most clients are medium to large corporations and government entities Shell Oil Southern California Edison Cisco Systems USC Drug Enforcement Administration (DEA) General Services Administration (GSA)

4 What We ll Cover Utilizing User-Defined Types Working with Constants Working with Arrays Passing by Reference Versus Passing by Value Using Optional Parameters Working with Empty and Null Creating and Working with Custom Collections

5 Utilizing User-Defined Types Also known as a struct or record Allows you to create a variable containing several pieces of information Generally used to house related information Each element can store a different type of data

6 Utilizing User-Defined Types Public Type TimeCardInfo TimeCardDetailID as Long TimeCardID as Long DateWorked as Date ProjectID as Long WorkDescription As String * 255 BillableHours As Double BillingRate as Currency End Type

7 Utilizing User-Defined Types Creating a Type variable Dim mtyptimecarddate as TimeCardInfo

8 Utilizing User-Defined Types Storing information from a record displayed on a form into a Type variable Private Sub cmdwritetotype mtyptimecarddata.timecarddetailid = Me.txtTimeCardDetailID mtyptimecarddate.timecardid = Me.txtTimeCardID. End Sub

9 Utilizing User-Defined Types Retrieving information from elements of a Type Private Sub cmddisplayfromtype_click MsgBox Timecard Detail ID Is & _ mtyptimecarddata.timecarddetailid & _ vbnewline & _ Time Card ID Is & _ mtyptimecarddata.timecardid

10 Working with Constants Symbolic Improve readability Make maintenance easier Self-documenting Intrinsic Built into the VBA language System-defined Available to all applications True, False, Null

11 Working with Constants Private Const mcurtaxrate as Currency =.0875 Private Const MTAXRATE as Currency =.0875 Function TotalAmount(curSaleAmount as _ Currency) TotalAmount = cursaleamount * MTAXRATE End Function

12 Working with Arrays Series of variables referred to by the same name Each element has a unique index number All elements must be of the same data type It is easy to loop through each element of an array, performing some process on each element

13 Working with Arrays Dim astrnames(5) as String Sub FixedArray() Dim astrnames(5) as String Dim intcounter as Integer astrnames(0) = Dan astrnames(1) = Alexis astrnames(2) = Brendan For intcounter = 0 to Ubound(astrNames) Debug.Print astrnames(intcounter) Next intcounter End Sub

14 Working with Arrays Sub FixedArray() Dim astrnames(5) as String Dim intcounter as Integer Dim vntany as Variant astrnames(0) = Dan astrnames(1) = Alexis astrnames(2) = Brendan For Each vntany in astrnames Debug.Print vntany Next vntany End Sub

15 Working with Arrays Sub DynamicArray() Dim astrnames() as String Dim intcounter as Integer Dim vntany as Variant Redim astrnames(2) astrnames(0) = Dan astrnames(1) = Alexis astrnames(2) = Brendan For Each vntany in astrnames Debug.Print vntany Next vntany End Sub

16 Working with Arrays Sub ResizeDynamic() Dim astrnames() as String Dim intcounter as Integer Dim vntany as Variant Redim astrnames(1) astrnames(0) = Dan astrnames(1) = Alexis Redim astrnames(2) astrnames(2) = Brendan For Each vntany in astrnames Debug.Print vntany Next vntany End Sub

17 Working with Arrays Sub ResizePreserve() Dim astrnames() as String Dim intcounter as Integer Dim vntany as Variant Redim astrnames(1) astrnames(0) = Dan astrnames(1) = Alexis Redim Preserve astrnames(2) astrnames(2) = Brendan For Each vntany in astrnames Debug.Print vntany Next vntany End Sub

18 Working with Arrays Passing Arrays as Parameters Sub PassArray() Dim astrnames(5) as String Dim intcounter as Integer Call FillNames(astrNames) For intcounter = 1 to Ubound(astrNames) Debug.Print astrnames(intcounter) Next intcounter End Sub Sub FillNames(varNameList as Variant) varnamelist(0) = Dan varnamelist(1) = Alexis varnamelist(2) = Dan End Sub

19 Passing By Reference Versus Passing By Value By default parameters are passed by reference This means that a memory reference to the variable is received by the function The function that is called can modify the value of the variable in the calling function

20 Passing By Reference Versus Passing By Value Sub PassByRef Dim strfirstname as String strfirstname = Alison Call FuncByRef(strFirstName) Debug.Print strfirstname End Sub Sub FuncByRef(strFirstParm as String) strfirstparm = Alan End Sub

21 Passing By Reference Versus Passing By Value Sub PassByVal Dim strfirstname as String strfirstname = Alison Call FuncByRef(strFirstName) Debug.Print strfirstname End Sub Sub FuncByVal(ByVal strfirstparm as String) strfirstparm = Alan End Sub

22 Using Optional Parameters Function ReturnInit(ByVal strfname as String, Optional ByVal strlname) If IsMissing(strLName) Then strlname = _ InputBox( Enter Last Name ) End If ReturnInit = strlname &, & _ strfname) End Function

23 Using Optional Parameters Function ReturnInit2(ByVal strfname as String, Optional ByVal strlname) If IsMissing(strLName) Then strlname = Balter End If ReturnInit2 = strlname &, & _ strfname) End Function

24 Using Optional Parameters Function ReturnInit3(ByVal strfname as String, Optional ByVal strlname) If IsMissing(strLName) Then ReturnInit3 = strfname Else ReturnInit3 = strlname &, & _ strfname End If End Function

25 Using Optional Parameters Function ReturnInit4(Optional ByVal strfname as String = Alison, Optional ByVal strlname as String = Balter ) ReturnInit3 = strlname &, & _ strfname End If End Function

26 Working with Empty and Null Working with Empty Variant variables are initialized to the value of Empty Once a value is placed in a variant variable, it is no longer empty

27 Working with Empty and Null Sub StringVar() Dim strname as String Debug.Print IsEmpty(strName) False Debug.Print strname = True End Sub Sub EmptyVar() Dim vntname as Variant Debug.Print IsEmpty(vntName) True vntname = Debug.Print IsEmpty(vntName) False vntname = Empty Debug.Print IsEmpty(vntName) True End Sub

28 Working with Empty and Null Sub EmptyVar() Dim vntname as Variant Debug.Print IsEmpty(vntName) True Debug.Print IsNull(vntName) False vntname = Null Debug.Print IsEmpty(vntName) False Debug.Print IsNull(vntName) True End Sub

29 Working with Empty and Null Function ReturnInit3(ByVal strfname as String, Optional ByVal strlname) If IsMissing(strLName) Then ReturnInit3 = strfname Else ReturnInit3 = strlname &, & _ strfname End If End Function

30 Working with Empty and Null Practical Examples LoopProjects LoopProjects2 Form_Current PropNulls

31 Creating and Working with Custom Collections Advantages over arrays Dynamically allocated Knows how many elements it has Each element can contain a different type of data You can insert elements anywhere you would like

32 Creating and Working with Custom Collections Dim colnames as Collection colnames.add Alexis, Alexis Sub AddToCollection() Dim colnames as Collection Set colnames = New Collection colnames.add Alison, Alison colnames.add Dan, Dan colnames.add Alexis, Alexis colnames.add Brendan, Brendan End Sub

33 Creating and Working with Custom Collections Accessing an item in a collection Debug.Print colnames.item(1) Debug.Print colnames(1) Debug.Print colnames( Alexis )

34 Creating and Working with Custom Collections Removing items from a collection Remove method colnames.remove 2 colnames.remove Alexis Set colnames = New Collection (all items) Set colnames = Nothing (all items)

Creating and Working with Custom Collections Iterating through the elements of a custom collection Sub IterateCollection() Dim colnames as Collection Dim varitem as Variant Set colnames = New

35 Creating and Working with Custom Collections Iterating through the elements of a custom collection Sub IterateCollection() Dim colnames as Collection Dim varitem as Variant Set colnames = New Collection colnames.add Alison, Ali colnames.add Daniel, Dan colnames.add Alexis, Lexie colnames.add Brendan, Bren For Each varitem in colnames Debug.Print colnames(varitem) Next varitem End Sub

DATABASE AUTOMATION USING VBA (ADVANCED MICROSOFT ACCESS, X405.6)

Technology & Information Management Instructor: Michael Kremer, Ph.D. Database Program: Microsoft Access Series DATABASE AUTOMATION USING VBA (ADVANCED MICROSOFT ACCESS, X405.6) AGENDA 3. Executing VBA