1. Advanced Programming Strings Arrays Arguments Modulus

2. Strings are NOT arrays Strings have no indexes Although arrays of strings have indexes A single string variable has no index Array indexes can have base of 0 or 1 Strings positions ALWAYS begin at 1 String functions report errors for position=0

3. Mid() function MyString = " Mid Function Demo " ' Create text string. FirstWord = Mid(MyString, 1, 3) ' Returns " Mid ". LastWord = Mid(MyString, 14, 4) ' Returns " Demo ". MidWords = Mid(MyString, 5) ' Returns " Function Demo ".

4. InStr() function strHaystack ="XXpXXpXXPXXP“ strNeedle = "p" intWhere = Instr(1, strHaystack, "W") Returns 0 intWhere = Instr(4, strHaystack, strNeedle) Returns 6

5. Other Functions Mid() statement (not the mid function) –strX = "Hello, Jane" ' example of mid() statement –Mid(strX, 8, 4) = "Bill“ (creates Hello, Bill) Left(strX,n) and Right() – returns L/R sections Ucase() and Lcase() – changes Up/Low case Trim(), Rtrim() and Ltrim() – removes blanks Len() – returns number of characters

6. Intro to Arrays Lists (e.g.,states, income levels, schedules) Private, Public, fixed or dynamic size! Example: –Dim strMonthNames(0 to 11) As String

7. strMonth(0) = "January" strMonth(1) = "February" strMonth(2) = "March" strMonth(3) = "April" strMonth(4) = "May" intInput = InputBox("Enter a month number (1-12)")-1 MsgBox “You entered “& strMonth(intInput) String example: base 0

8. Which Array to Go? Option Base 1 or Option Base 0? Public strState(0 to 49) As String Public strState(1 to 50) As String Public strState(50) As String

9. Flexible Array Dynamic Dim curLevel() As Currency Expands and contracts Good for uncertain run-time conditions Can loose contents unless… –Redim Preserve curLevel(7) Can erase dynamic arrays: Erase curLevel

10. Multidimensional arrays Referencing locations by field and record Example Dim varDataSet(0 to 4, 0 to 9) 5 fields (columns) 10 records (rows) First field of the last record: varDataSet(0,9)

11. Multidimensional arrays This array has 6 columns and 7 rows : Dim varContributor(0 to 5,0 to 6) as variant Columns before rows (alpha order) June Nguyen's contribution is varContributor(5,2) Think of multidimension arrays as datasheets.

12. Sizing up arrays Your subs and functions will be more reusable if they work for any size arrays. Lbound(),Ubound() return lower, upper bound of one dimension, regardless of BASE. Lbound(varData, 1 or 2),Ubound(varData, 1 or 2) –Use 1 for fields count (columns – first again) –Use 2 for records count (rows – second again) How many columns are there in varData? –Ubound(varData,1) – Lbound(varData,1) + 1

13. Example: summarize salaries Dim curSalary(0 to 7, 0 to 10) If column 7 of this array is $ salary Summarize the salaries For intRow = Lbound(curSalary,2) to Ubound(curSalary,2) curSum = curSum + curSalary(7, intRow) intN = intN + 1 Next MsgBox "Total Amount=" & Format(curSum,"Currency") MsgBox "Average Amount=" & Format( _ iif(intN>0,curSum/intN,0), "Currency")

14. Memory Considerations strAbsentMinded(0 to 9) uses 22 times less memory than varAbsentMinded(1 to 10) when they hold the identical data intArray(0 to 9, 0 to 19, 0 to 29) reserves 6,000 integer locations, or about 12,000 (plus) bytes. 10 * 20 * 30 = 6,000 * 2 bytes/integer = 12,000 bytes

15. Parameter Arrays in Procs Extremely useful and powerful The arguments are treated as one array VBA forces Option Base 0, so use Lbound() and Ubound() Example: a general utility to calculate class averages on quizzes, exams, and assignments after dropping your lowest score. The number of scores is unpredictable.

16. Parameter Arrays: Example Function DropAvg(ParamArray varScore() as Variant) as Variant Dim varAverage as Variant, varLowest as Variant Dim varValue as Variant ' requires at least two scores in the array varLowest = 99999 if UBound(varScore, 1)<= 0 then DropAvg=0 : Exit Function For Each varValue in varScore varAverage = varAverage + varValue If varValue < varLowest then varLowest = varValue Next DropAvg = (varAverage - varLowest) / UBound(varScore, 1) End Function Do this to test in the immediate window: ?DropAvg(95,93,87,91,81) ' notice arguments 91.5 ?DropAvg(71,85) 85 See next slide to compare Param array args to plain array args

17. Arrays: Example Function DropAverage(dblScore() As Double) As Variant Dim varAverage As Variant, varLow As Variant Dim varValue As Variant, intI As Integer, intCount As Integer ' requires at least two scores in the array varLow = 99999 intCount = UBound(dblScore, 1) - LBound(dblScore, 1) If intCount <= 0 Then Exit Function For intI = LBound(dblScore, 1) To UBound(dblScore, 1) varAverage = varAverage + dblScore(intI) If dblScore(intI) < varLow Then varLow = dblScore(intI) Next DropAverage = (varAverage - varLow) / intCount End Function Do this to test in the immediate window: Public Sub XX() Dim dblData(0 To 2) As Double dblData(0) = 85.6: dblData(1) = 90.2: dblData(2) = 92.1 Debug.Print DropAverage(dblData) ' notice arg is an array End Sub

18. Creating Arrays The Array function Your Option Base is observed Option Base 0 Public Function DayOfWeek(intDay As Integer) As String Dim WeekDay As Variant WeekDay = _ Array("Sun","Mon","Tue","Wed","Thu","Fri","Sat") DayOfWeek = WeekDay(intDay) End Function In the Immediate Window ?DayOfWeek(1) Mon

19. Creating Arrays The GetRows Method Forces Option Base 0 Public Function Sum() Dim intRow as Integer, intN as Integer Dim varDataSet() As Variant Dim cnn As ADODB.Connection Set cnn = CurrentProject.Connection rst.Open "tblEmployee", cnn, adOpenDynamic,, adCmdTable varDataSet = rst.GetRows rst.Close For intRow = LBound(varDataSet, 2) To UBound(varDataSet, 2) Sum = Sum + varDataSet(3, intRow) : intN = intN+1 Next Sum = iif(intN > 0,Sum/intN, 0) Debug.Print "Average Amount=" & Format( Sum, "Currency") End Function

20. Detecting what data is in a Variant VarType(variable) TypeName(variable) Useful for detecting –Calculation data –Arrays (VarType=8192+) –Valid dates

21. Receiving Arguments Default is by reference (ByRef) –Send the address of the argument –The contents of the address can be changed by either the caller or the procedure. Option is by value (ByVal) –Send a copy of the argument –The variable cannot be changed by the proc because it only has a copy.

22. Receiving Arguments: Example ' build in the protection at design time (formal args) Sub AllNames (ByVal BothNames as String, ByRef LastName as String, ByRef FirstName as String) ' or use this actual argument format at run time ' it forces ByVal and sends a copy of the variable Call AllNames ((Names), First, Last) ' But, an array cannot be passed ByVal Call Average (varDatSet, 6)

23. Type structure A named data structure Place in Declarations Module Instantiate when needed Result: A data object

24. Type ContributionFormError FirstName As Boolean LastName As Boolean Date As Boolean Party As Boolean Sex As Boolean Amount As Boolean End Type Define the structure in the Declarations Module

25. ' create a module-level structure in ' the Declarations section of your Form Module Private ErrorIn As ContributionFormError ' in the error checking code set these flags ErrorIn.FirstName = True ErrorIn.Amount = True ' example on next slide shows 1.Passing a data structure as an argument 2.Use of the With…End structure Instantiate ErrorIn structure in the Form Module

26. MsgBox "The following errors must be corrected:" & vbCR & _ ErrorList(ErrorIn)",vbExclamation,"Mayor Minimum" Function ErrorList(AnyErr As ContributionFormError) As String With AnyErr If.FirstName Then ErrorList = ErrorList + vbCr & "First Name" If.LastName Then ErrorList = ErrorList + vbCr & "Last Name" If.Party Then ErrorList = ErrorList + vbCr & "Party" If.Sex Then ErrorList = ErrorList + vbCr & "Sex" If.Date Then ErrorList = ErrorList + vbCr & "Date" If.Amount Then ErrorList = ErrorList + vbCr & "Amount" End With End Function Use the structure to build a message

27. Use the structure to build a better message If IsError(ErrorIn) Then MsgBox "There are " & _ IsError(ErrorIn) & " errors." & vbCR & _ ErrorList(ErrorIn)",vbExclamation,"Mayor Minimum" Private Function IsError(ErrorStructure As _ ContributionFormError) As Integer IsError = 0 If ErrorStructure.FirstName Then IsError = IsError + 1 If ErrorStructure.LastName Then IsError = IsError + 1 If ErrorStructure.Party Then IsError = IsError + 1 If ErrorStructure.Sex Then IsError = IsError + 1 If ErrorStructure.Date Then IsError = IsError + 1 If ErrorStructure.Amount Then IsError = IsError + 1 End Function

28. Modulus VBA and many other languages have this built in function for finding the remainder of a division. For example, 5 mod 2 equals 1 (5/2=2 with 1 left over) 6 mod 2 equals 0 (6/2=3 with 0 left over) anynumber mod 2 = 1 if anynumber is odd anynumber mod 2 = 0 if anynumber is even Odd and even are the usual reasons for programming with mod. And there is another handy use for the function: controlling sequences by limiting the range of a counter.

29. Using the Modulus : Sequencing Mod is also useful when you want to limit a series of numbers to a range. Say you want users to be presented with a sequence of three choices, or five choices, or seven choices and not do a lot of programming logic. choice = 1 + (choice mod N) The line of code above will limit the values taken on by the variable choice. They will be in the range of 1, 2,…, N. The starting value of choice has to be inside the particular range. An example is next.

30. Using the Modulus : Program Example Public Sub RangeOfChoices() ' initialize the variables Dim strChoice(1 to 3) As String Dim intChoice As Integer Dim intTrip As Integer intChoice = 1 strChoice(1) = "the beach?" strChoice(2) = "the mountains?" strChoice(3) = "Philadelphia?" ' body of your logic Do intTrip = MsgBox("Would you like to go to " & _ strChoice(intChoice), vbYesNo, "This Summer") intChoice = (intChoice Mod 3) + 1 Loop Until intTrip = vbYes End Sub