References. Parameters revisited. Reference Parameters. Example: Swapping values. Named Arguments

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1 References ENGG1811 Computing for Engineers Week 7 Objects and Collections; Using the Macro Recorder; Shapes Chapra (Part 2 of ENGG1811 Text) Topic 10 (chapter 3) Macro Recorder ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 1 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 2 Parameters revisited Values passed to procedures are called arguments Variables defined to hold these values are called parameters Parameters are local variables, like ones declared using Dim Data can be passed in two different ways: by value (argument is expression, only value transferred) by reference (argument is variable, parameter acts as a temporary alias) keywords ByVal and ByRef specify which (ByRef is assumed if omitted) Reference Parameters Sub halve1(byval x As Double) x = x / 2 Sub halve2(byref x As Double) x = x / 2 y = 6.4: z = 6.4 halve1 y ' what is the value of y? halve2 z ' what is the value of z? The keyword ByRef (or none) passes a reference to the argument rather than its value. x becomes an alias for z and changes to x also affect z immediately. With ByVal, or if the argument is not a variable, x is an independent local variable initialised by the argument (6.4). Changing it has no effect outside the procedure. ENGG1811 UNSW, CRICOS Provider No: 00098G W6 slide 3 ENGG1811 UNSW, CRICOS Provider No: 00098G W6 slide 4 Example: Swapping values Sub Swap(ByRef x1 As Variant, ByRef x2 As Variant) Dim dbltemp As Variant dbltemp = x1 x1 = x2 x2 = dbltemp y = -23.5: z = 6 Swap y, z ' what are the values of y and z? We used the Variant type so the procedure can be used to exchange the contents of variables any type. This is the only recommended use for Variants. Unfortunately, the following does NOT work Swap ActiveSheet.Cells(1,1), ActiveCell Motivation: imagine exchanging the positions of an apple and an orange on the table in front of you. Now do it again using just one hand! Named Arguments For procedures with long argument lists (especially built-in procedures), arguments can be specified in any order using the notation paramname:=argument Example (see MsgBox Function in VBA Help) reply = MsgBox(title:="Bummer", _ returns integer value representing button pressed: vbcancel or vbretry prompt:="no solution to your equation", _ buttons:=vbcritical + vbcancelretry) parameter name underscore allows line break within statement built-in VBA constants assist readability ENGG1811 UNSW, CRICOS Provider No: 00098G W6 slide 5 ENGG1811 UNSW, CRICOS Provider No: 00098G W6 slide 6 1

2 Arrays Default array bounds Arrays are groups of variables of the same type Each element of an array has a unique index, representing its position in the array, usually starting at 0 or 1 Declaration specifies type and bounds: Const MAX_SAMPLES = 10 Const ALPHA_SIZE = 26 Const MONTHS_PER_YEAR = 12 Dim dblsamples(1 To MAX_SAMPLES) As Double Dim freq(0 To ALPHA_SIZE-1) As Integer ' letter frequencies Dim daysin(1 To MONTHS_PER_YEAR) As Integer ' days in each month If the lower bound is omitted, a default value is used The default value is normally 0 Can be changed with Option Base directive at top of module Option Base 1 ' omitted lower bounds now = 1 Const MAX_SAMPLES = 200 Dim dblsamples(max_samples) As Double ' valid index 1..MAX_SAMPLES Recommended approach: specify both bounds ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 7 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 8 Array usage Arrays and Cells Arrays are often visualised as a line of variables: daysin index Access a particular element using the array name and an index expression in parentheses Dim idx As Integer Dim dblsample(1 To MAX_SAMPLE) As Double ' load array from first column of worksheet For idx = 1 To MAX_SAMPLE dblsample(idx) = ActiveSheet.Cells(idx,1).Value Next idx For statement mimics array declaration The Excel model allows access to worksheet cells as a two-dimensional array ActiveSheet.Cells(row,col).Value = 42 Arrays are a more general programming structure, independent of the application's user-accessible data like worksheets and documents Arrays are not visible like cells, can be used for intermediate storage Like other variables, can be local to a module or to a procedure. ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 9 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 10 Objects VBA is a mixture of conventional procedural notation process dataobject or evaluate(dataobject) and object oriented programming dataobject.method Excel data is represented by objects that have properties and to which methods are applied: Methods are procedures that are associated with a type of object and are applied to objects of that kind array representing all rows ActiveSheet.Cells(row,col).Formula = "=B3/4" ActiveSheet.Hide applies the Hide method to the active sheet ActiveSheet.Rows(2).Clear second element (= row 2) row = ActiveCell.Row assigns to the Formula property of the cell applies the Clear method to the object (row 2 of the active sheet) property recording the row number of the active cell ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 11 Objects, continued Most important object types are Application one instance representing the Excel state, provides methods to create dialogue boxes and other window objects Workbook Worksheet Range any single cell or group of cells The on-line manual describes their properties and methods, but the Macro Recorder (later slide) allows us to see what object manipulation corresponds to particular user interaction ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 12 2

3 Collections Collections, continued Array concept relies on strict ordering of elements If elements can be named, get more general way of describing the group A Collection is an array-type object indexed either by number or by name Properties include: Count (number of elements) Methods include: Add (a named element, relatively positioned) Item (retrieve "current" element) Some Excel objects are collections Application.Workbooks ' (base type: Workbook) Application.ActiveWorkbook.WorkSheets ' (Worksheet) ActiveWorkbook.Sheets ' (Chart or Worksheet) ActiveSheet.Charts ' Displayed charts ActiveSheet.Shapes ' Drawing objects: later slide Examples Sheets.Add Name:="New sheet", After:=Sheets(3) Debug.Print Sheets(1).Name (in full: Debug.Print Application.ActiveWorkbook.Sheets(1).Name) Debug.Print Workbooks.Count ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 13 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 14 Manipulating Collections Declare variable to reference elements Dim wks As Worksheet Object assignment uses the Set keyword Set wks = Sheets(1) this is easy to forget Access object properties and methods: wks.columns(col).clear ' property/method wks.unhide ' method wks.cells(row,col).formula = "=A1+1" Iterating over a Collection Special notation to iterate over elements: For Each wks In ActiveWorkbook.Sheets Debug.Print wks.name Next wks Equivalent (but preferable) to: For idx = 1 To ActiveWorkbook.Sheets.Count Set wks = Sheets(idx) Debug.Print wks.name Next idx ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 15 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 16 With Statement Sometimes the same object needs to be referenced several times in succession ActiveSheet.Cells(row,col) = intval1 ActiveSheet.Cells(row+1,col) = intval2 ActiveSheet.Cells(row+2,col) = intval3 Use a With statement for the common prefix: With ActiveSheet.Cells(row,col) = intval1.cells(row+1,col) = intval2.cells(row+2,col) = intval3 note dot is retained in the shortened reference Note The following topics contain a lot of detail Most of the info can be found in Help screens or reference books You don t have to learn the detail, but you must understand the way that these structures are put together Lab work will guide you through the essential skills needed to manipulate objects, including referencing ranges using the macro recorder creating and manipulating drawings but you need to follow what s presented here! ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 17 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 18 3

4 Ranges Some Range Properties The Range type represents a rectangular group of (one or more) cells on a worksheet Can be referred to in many ways Single cell, separate indexes:.cells(row,col) Single cell, RC format:.range("b5") Single row, index:.rows(row) Single column, index:.column(col) Row/column block:.rows("4:6").columns("a:c") Any block, RC format:.range("b4:h7") Named range:.range("polynomial") Derived from another range: ActiveCell.EntireRow Whole sheet:.cells Borders Object representing outline Comment Comment text Font Text font Formula Formula as a string (such as "=A$1/24") Height, Width Height or width in screen units HorizontalAlignment xlleft/xlcenter/xlright Interior Object representing cell background Left, Top Position of range on sheet, in screen units Locked True Cells can't be changed by the user Name Name if defined NumberFormat Name or specification of display format Value Stored value Note: Properties of a multi-cell range are undefined if the cell properties are not consistent ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 19 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 20 Some Range Methods AutoFilter Apply column filters Calculate Re-evaluate formulae Clear, ClearComments Remove cell contents or comments Copy, Cut Copy to clipboard, Cut=remove after pasting Delete Remove cells and shift in FillDown, FillRight Apply fill operations Find Search for cell contents matching value Offset Generate reference to nearby cell GoalSeek Apply Excel's Goal Seek (range must be one cell) Merge Merge cells, retaining value from top left cell PasteSpecial Paste from Clipboard with optional transforms Replace Replace cell contents Select Make range the current selection (available as the Selection object) Sort Reorder rows (has many parameters) Range as a Collection ' From an example at ' use in worksheet: =SumIfColoured(A1:C6) Function SumIfColoured(rngCells As Range) As Double Dim cell As Object Dim sum As Double sum = 0 For Each cell In rngcells If cell.interior.colorindex <> xlnone Then sum = sum + Cell.Value End If Next cell SumIfColoured = sum End Function ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 21 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 22 Macro Recorder Using the Macro Recorder Almost everything the user can do with Excel can be tracked as a Macro and replayed* Macros are stored as VBA procedures Macros can be edited (or cannibalised!) to adapt or generalise their purpose Effective way to find out how to achieve a particular effect (especially as VBA Help is poor) * unfortunately, Excel 2007 does not record drawing operations, whereas Excel 2003, 2002 and 2000 did. PowerPoint 2007 doesn t record anything at all, whereas PPT 2003, 2002 and 2000 did. Excel 2008 for Macintosh doesn t even have VBA, whereas 2004 for Mac did. Do you see a pattern of behaviour by Micro$oft here? Menu path Developer Record Macro (Tools Macro Record New Macro for Excel 2003) Name, location, description and optional shortcut key can be set. Creates new module if necessary Tracks all menu functions and relevant mouse activity (cell selections, dialogue responses, etc) When finished, Developer Stop Recording View/edit macro with VBE ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 23 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 24 4

5 Macro Recording conventions Example: Cell operations Use of Select method and Selection object since the user has to identify an element before doing anything to it Use of With Selection... Sets all properties of an object, even if only one was changed Uses Range() and related objects extensively Uses absolute references, where a programmer would use a variable or constant (hence readability is poor) Apply the following to a two-column table such as the solution to Lab 6 Part C: 1. Adjust the alignment and indent of column B; 2. Change the background of the header cells 3. Change the font weight and colour of the header cells ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 25 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 26 VBA Created by Recorder Colour Representation Columns("B:B").Select With Selection.HorizontalAlignment = xlright.verticalalignment = xlbottom.wraptext = False.Orientation = 0.AddIndent = False.ShrinkToFit = False.ReadingOrder = xlcontext.mergecells = False Selection.InsertIndent 1 Range("A1:B1").Select With Selection.Interior.Pattern = xlsolid.color = 192 Selection.Font.Bold = True With Selection.Font.Color = ' other font changes Colour info next slide Change properties using the Selection object Shows all properties, even though we only changed HorizontalAlignment Prior to 2007 Excel stored cell colours as one of 56 standard values (ColorIndex). This still works introduced themes, but can store RGB (red, green, blue) values too.color is a Long integer, derived from R, G, B components (each ) code = 1*red + 256*green + 256*256*blue Example: dark brown is R=200, G=100, B=0 COL_DKBROWN = *100 = better: use RGB function Selection.Font.Color = RGB(200, 100, 0) ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 27 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 28 Recorder vs Human ❶ The Macro Recorder makes extensive use of the Selection object (since the user must select elements before using them) Humans can refer directly to the affected object: Const COL_DATA = 2 With Columns(COL_DATA) ' = Columns("B:B").HorizontalAlignment = xlright ❷ Humans can code iteration, Recorder can't ❸ Humans can use local variables, Recorder can't ❹ Humans can use Const definitions and meaningful names, Recorder can't Shapes The Office family supports drawing operations, including lines, filled polygons, predefined shapes Represented by Shape objects, thus can be manipulated by VBA To create a drawing with Excel: View tab, uncheck Gridlines (and/or Headings) Insert tab Shapes Lines, rectangles, circles, stroke and fill etc on palette Connectors are especially useful as they snap to vertices Can no longer use Macro Recorder to create sample code! Separate Drawing with VBA documentation/tutorial provided for you instead: see website. ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 29 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 30 5

6 Shapes in VBA Coordinate system is Cartesian (which way is Y?) Units are points (1/72 inch, approx 28 pts per cm) Drawing elements are members of the Shapes collection belonging to the active sheet New shapes are created using methods (built-in procedures) with distinctive args for shape type and characteristics Many shape types (type AutoShapeType to Help, then click on msoautoshapetype for list) Changes to properties with user interface is via Selection object (though not required in VBA) Identifying Shapes Create most shapes with Dim shp As Shape Set shp = ActiveSheet.Shapes.AddShape(type, _ left, top, width, height) Set shp = ActiveSheet.Shapes.AddTextbox( ) ' then use shp to set properties Each shape is given a name and number according to its type ("Rectangle 1", "AutoShape 5"), and each has an index, equal to the collection size after Add lastshape = ActiveSheet.Shapes.Count Can later use the index to reference the shape: ActiveSheet.Shapes(lastShape) Keeping track of all shapes this way can be tricky (but arrays help) ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 31 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 32 Shape Operations Applying stroke (outline) With object.line.weight = 1.5 ' in points.style = msolinesingle ' default.dashstyle = msolinesquaredot.forecolor.rgb = RGB(0,0,128) ' dark blue stroke Also BeginArrowheadStyle; Width (Wide/Medium/Narrow) as well as Length (Long/Medium/Short).EndArrowheadStyle = msoarrowheadtriangle.endendarrowheadlength = msoarrowheadlengthmedium Applying fills.fill.forecolor.rgb = RGB(red, green, blue) ' Fill.Transparency = 0# ' 0# = 0.0 (VB idiom).fill.visible = False ' to hide (also.line) Text Boxes Text is held in boxes (with stroke and fill) object.characters.text = "Power Station" With object.characters.font.name = "Arial Narrow".FontStyle = "Bold".Size = 11 Font properties of substrings object.characters(start:=3, Length:=2) _.Font.Subscript = True Remove box:.fill.visible = False.Line.Visible = False ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 33 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 34 Examples (Wed 2pm) Summary 1. Colour Picker (using RGB codes from a sheet) 2. Programming with shapes: Venn Diagram Algorithm is simple (but calcs are fiddly) Draw canvas Calculate geometry Draw first set Draw second set Draw labels (4 sub calls) Draw pointer Reference parameters allow a subprogram to change the value of variables declared outside Arrays store a sequence of multiple values Array elements are indexed by a small integer Collections store a set or sequence of objects, referenced by either name or index Objects enable access to complex data managed by the application A Range object represents part of a worksheet, can also be viewed as a collection of cells Macro recorder creates editable VBA from user interaction with the application ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 35 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 36 6

7 Array example For any date, calculate the day of the year (1 Jan = day 1, 31 Dec = day 365 or 366) as used in business and financial systems Analysis: the day of the year = the number of days in all the previous months, plus the day of the month. For example, in a non-leap year, Anzac Day (25 April) is day ( ) + 25 = 115. Leap year adjustment: add 1 to day if past February in a leap year. That's all. Programming: use an array to hold the days in each month (constants), accumulate sums Pseudocode Given variables day, month, year: Initialise daysin array Set sum to the sum of the days in all months < month Add day to sum If year is a leap year And month > February Add 1 to sum result is stored in sum The step Set sum is a substantial subtask with its own pseudocode (written as a function) Set s to 0 For each m from 1 to month-1 add daysin(m) to s return the value in s ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 37 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 38 Initialising the daysin array Unfortunately VBA doesn't support constant arrays, or allow direct assignment of arrays. However, it does have a function that constructs an array and returns it as a Variant, which can be indexed Private Sub InitDaysIn() Dim constlist as Variant Dim m As Integer You don't need to know this, it's just to make the demo work constlist = Array(31, 28, 31, 30, 31, 30, _ 31, 31, 30, 31, 30, 31) For m = 1 To MONTHS_PER_YEAR daysin(m) = constlist(m) Next m Partial solution Function DaysToEndOf(month As Integer) As Integer Dim m As Integer ' a month number Dim s As Integer ' sum of days in 1..m s = 0 For m = To s = Next m DaysToEndOf = s ' return answer End Function Complete solution left as an exercise. Use a leapyear function and a named constant for February. ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 39 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 40 Resizing Arrays Arrays can be dynamically sized if needed with this statement (not declaration): Redim Preserve dblsample(1 To 10*MAX_SAMPLE) Preserve retain elements up to new limit Current array bounds are returned by the built-in functions LBound(arr) and UBound(arr): For idx = LBound(dblSample) To UBound(dblSample) dblsample(idx) = dblsample(idx) / 2 Next idx ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 41 7