Mark Dixon, SoCCE SOFT 131Page 1 10 – Enumerated Data Types & Procedure Parameters.

Mark Dixon, SoCCE SOFT 131

10 – Enumerated Data Types & Procedure Parameters


Session Aims & Objectives• Aims, to introduce:

– the idea of enumerated data types– passing parameters/arguments to procedures– control arrays

• Objectives, after this week’s sessions, you should be able to:

– declare and use an enumerated data type– use parameters in your programs to make

procedures more flexible– use control arrays


Enumerated Data Types• Often need to use numbers to represent

things (coding)

• For example, curry: mild, medium, or hot• Could store text: "mild", "medium", "hot"

– takes lots of space (1 byte per character)– easily becomes inconsistent, e.g. "hit“ vs. “hot”

• Alternatively, use numbers to represent text:1 "mild"2 "medium"3 "hot"


Example: Curry v1Option Explicit

Private Sub Form_Load() lstCurry.AddItem "Mild", 0 lstCurry.AddItem "Medium", 1 lstCurry.AddItem "Hot", 2 picCurry.FillStyle = vbSolidEnd Sub

Private Sub lstCurry_Click() lblCurryCode.Caption = lstCurry.ListIndex lblCurryText.Caption = lstCurry.List(lstCurry.ListIndex) If lstCurry.ListIndex = 0 Then picCurry.FillColor = vbWhite ElseIf lstCurry.ListIndex = 1 Then picCurry.FillColor = vbYellow Else picCurry.FillColor = vbRed End If picCurry.Cls picCurry.Circle (1000, 750), 500End Sub

Curry v1



Private Sub Form_Load() lstCurry.AddItem "Mild", 0 lstCurry.AddItem "Medium", 1 lstCurry.AddItem "Hot", 2 picCurry.FillStyle = vbSolidEnd Sub

Private Sub lstCurry_Click()Dim CuCo As Long ' Curry code CuCo = lstCurry.ListIndex lblCurryCode.Caption = CuCo lblCurryText.Caption = lstCurry.List(CuCo) If CuCo = 0 Then picCurry.FillColor = vbWhite ElseIf CuCo = 1 Then picCurry.FillColor = vbYellow Else picCurry.FillColor = vbRed End If picCurry.Cls picCurry.Circle (1000, 750), 500End Sub

Curry v2



Const Mild = 0Const Medium = 1Const Hot = 2 Private Sub Form_Load()

lstCurry.AddItem "Mild", Mild lstCurry.AddItem "Medium", Medium lstCurry.AddItem "Hot", Hot picCurry.FillStyle = vbSolid End Sub

Private Sub lstCurry_Click() Dim CuCo As Long ' Curry code CuCo = lstCurry.ListIndex lblCurryCode.Caption = CuCo lblCurryText.Caption = lstCurry.List(CuCo) If CuCo = Mild Then picCurry.FillColor = vbWhite ElseIf CuCo = Medium Then picCurry.FillColor = vbYellow Else picCurry.FillColor = vbRed End If picCurry.Cls picCurry.Circle (1000, 750), 500 End Sub

Curry v3



Enum TSpice Mild = 0 Medium = 1 Hot = 2End Enum Private Sub Form_Load() lstCurry.AddItem "Mild", Mild lstCurry.AddItem "Medium", Medium lstCurry.AddItem "Hot", Hot picCurry.FillStyle = vbSolid End Sub

Private Sub lstCurry_Click() Dim CuCo As TSpice ' Curry code CuCo = lstCurry.ListIndex lblCurryCode.Caption = CuCo lblCurryText.Caption = lstCurry.List(CuCo) If CuCo = Mild Then picCurry.FillColor = vbWhite ElseIf CuCo = Medium Then picCurry.FillColor = vbYellow Else picCurry.FillColor = vbRed End If picCurry.Cls picCurry.Circle (1000, 750), 500 End Sub

Curry v4


Questions: EDTs• Create an EDT to store the following

classification of height: short, average, tall

• Create an EDT to store the following classification of publication: book, journal

Enum THeight Short = 0 Average = 1 Tall = 2End Enum

Enum TPublication Book = 0 Journal = 1End Enum


Parameters in Event Procedures• Provide us with information about event

– e.g. if mouse was clicked• where was it (x, and y co-ordinates)• which mouse button was pressed• which keyboard buttons were pressed ([Shift] / [Ctrl])


Example: Draw

Option Explicit

Private Sub picDraw_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) If Button = 1 Then picDraw.PSet (X, Y) End IfEnd Sub

Private Sub picDraw_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single) If Button = 1 Then picDraw.Line -(X, Y) End IfEnd Sub

• Parameters:– appear in the brackets of a procedure definition

horizontal & verticalmouse co-ordinates

mousebutton

keyboard[Shift] [Ctrl] keys


Parameters/Arguments (what)• Sometimes our own procedures need

information– Making a cup of tea:

• milk, and number of sugars

• Makes them more flexible

Make cupof tea

Milk

Sugars


Parameters (how)• Procedure Declaration

– Formal parameters define name & type

• Procedure Call– actual parameters list values in order

Option ExplicitDim res As Long

Private Sub Calc(Num1 As Long, Num2 As long) res = Num1 * Num2 End Sub

Private Sub btnCalc_Click() Calc 5, 2 Calc 11, 15 End Sub


Parameters (how)


Example: House v1Option Explicit

Private Sub btnDraw_Click()

picHouse.Cls

picHouse.Line (1000, 1000)-(2000, 1750), , B

picHouse.Line (1000, 1000)-(1500, 750)

picHouse.Line -(2000, 1000)

End Sub

House v1


Example: House v1 to v2

Option Explicit


picHouse.Cls

picHouse.Line (1000, 1000)-(2000, 1750), , B

picHouse.Line (1000, 1000)-(1500, 750)


End Sub

Option Explicit

Private Sub DrawHouse()

picHouse.Line (1000, 1000)-(2000, 1750), , B

picHouse.Line (1000, 1000)-(1500, 750)


End Sub


picHouse.Cls

DrawHouse

DrawHouse

DrawHouse

End Sub

House v1 House v2



Private Sub DrawHouse()

picHouse.Line (1000, 1000)-(2000, 1750), , B

picHouse.Line (1000, 1000)-(1500, 750)


End Sub


picHouse.Cls

DrawHouse

DrawHouse

DrawHouse

End Sub

House v2



Private Sub DrawHouse(x As Single, y As Single)

picHouse.Line (x, y)-(x + 1000, y + 750), , B

picHouse.Line (x, y)-(x + 500, y - 250)

picHouse.Line -(x + 1000, y)

End Sub


picHouse.Cls

DrawHouse 1000, 1000



End Sub

House v3


Questions: Parameters• Given the following declaration:

• What will the following put in lblOutput?

Sub thing(Num1 As Long, Num2 As Long, Num3 As Long)Dim tmpOutput As Long tmpOutput = (Num1 + Num2) * Num3 lblOutput.Caption = tmpOutputEnd Sub

thing 2, 3, 6thing 6, 3, 2thing 20, 5, 2

301850


Example: Till v1Option Explicit

Dim SubTotal As Double

Dim Total As Double

Private Sub btnEquals_Click()

Dim price As Double

Dim quantity As Double

price = Val(Me.txtPrice.Text)

quantity = Val(Me.txtQuantity.Text)

SubTotal = price * quantity

lblSubTotal.Caption = "£" & SubTotal

End Sub

Private Sub btnAdd_Click()

Total = Total + SubTotal

lblTotal.Caption = "£" & Total

End Sub

Private Sub btnUndo_Click()

Total = Total - SubTotal

lblTotal.Caption = "£" & Total

End Sub

Till v1


amount: Double

Example: Till v2Option ExplicitDim SubTotal As DoubleDim Total As Double

Private Sub TotalAdd(amount As Double) Total = Total + amount Me.lblTotal.Caption = "£" & Total End Sub

Private Sub btnEquals_Click() Dim price As Double Dim quantity As Double price = Val(Me.txtPrice.Text) quantity = Val(Me.txtQuantity.Text) SubTotal = price * quantity lblSubTotal.Caption = "£" & SubTotal End Sub

Private Sub btnAdd_Click() TotalAdd SubTotal End Sub

Private Sub btnUndo_Click() TotalAdd -SubTotal End Sub

TotalAdd

Till v2


Example: Heart Rate v3Option ExplicitDim HR(0 To 6) As Long

Private Sub Form_Load() HR(0) = 134 HR(1) = 127 HR(2) = 139 HR(3) = 155 HR(4) = 143 HR(5) = 151 HR(6) = 141End Sub

Private Sub DrawHR()Dim i As Long picMain.Cls For i = 0 To 6 picMain.Line -(i * 500, HR(i) * 10) NextEnd Sub

Private Sub btnDraw_Click() DrawHREnd Sub


Example: Heart Rate v4Option ExplicitDim HR(0 To 6) As Long

Private Sub Form_Load() HR(0) = 134 HR(1) = 127 HR(2) = 139 HR(3) = 155 HR(4) = 143 HR(5) = 151 HR(6) = 141End Sub

Private Sub DrawHR(picTemp As PictureBox)Dim i As Long picTemp.Cls For i = 0 To 6 picTemp.Line -(i * 500, HR(i) * 10) NextEnd Sub

Private Sub btnDraw_Click() DrawHR Me.picMain1 DrawHR Me.picMain2End Sub


Control Arrays• Several controls have same name

• Distinguished by unique index

• Very similar to a variable array

• Makes it easier to do same thing to all controls – using for loop


Example: Ships - UI

lblMooringID

picMain(3)

picMain(1)

picMain(2)

picMain(0)

• Four controls share same name (picMain):

Ships


Example: Ships - CodeOption Explicit

Sub Draw()Dim i As Long For i = 0 To 3 picMain(i).DrawWidth = 3 picMain(i).Line (1000, 1000)-(2000, 1000) picMain(i).Line -Step(-200, 200) picMain(i).Line -Step(-600, 0) picMain(i).Line -Step(-200, -200) NextEnd Sub

Private Sub picMain_Click(Index As Integer) lblMooringID.Caption = Index DrawEnd Sub


Control Arrays - How• To create a control array, either:

– Create a control with the same name as an existing control (VB will ask you if you want to create a control array)

Or:– Create a control and type a value into its index

property (e.g. 0)


Container Controls• Some controls can contain other controls:

– Picture boxes– Frames

• The container (parent) control clips the contained (child) controls– The child controls will not be displayed outside

the boundary of their parent


Example – Pic Container• The inner picture box is clipped:

picInner

picOuter


Tutorial Exercise: Curry• LEARNING OBJECTIVE:

to understand enumerated data types

• Task 1: Get the Curry examples from the lecture working.• Task 2: Modify your code – add an extra category called

‘Blazing’ with a code value of 3.


Tutorial Exercise: Draw• LEARNING OBJECTIVE:

– use parameters provided by event procedures

• Task 1: Get the Draw example (from the lecture) working.• Task 2: Modify your code – allow the user to rub out (paint

in the background colour) using the right mouse button.• Task 3: Modify your code – allow the user to use a thicker

line by holding down the [ctrl] button on the keyboard


Tutorial Exercise: House• LEARNING OBJECTIVE:

– use parameters in your own procedures, to make them more flexible (general purpose)

• Task 1: Get the House examples (versions 1, 2, and 3) from the lecture working.

• Task 2: Modify your code – add code that draws a door and a window for each house.

• Task 3: Modify your code – add code that draws 10 small houses. Hint: use a for loop (rather than simply copying the procedure calls)


Tutorial Exercise: Till• LEARNING OBJECTIVE:


• Task 1: Get the Till examples (versions 1 and 2) from the lecture working.

• Task 2: Modify your code – add code that clears all data when the clear button is clicked.

• Task 3: Modify your code – create a procedure to calculate and display the sub total.


Tutorial Exercise: Heart Rate• LEARNING OBJECTIVE:


• Task 1: Get the Heart Rate examples (versions 3 and 4) from the lecture working.

• Task 2: Modify your code – use additional parameters to control the horizontal and vertical sizes of the graphs (so that the two graphs can be different sizes).

Mark Dixon, SoCCE SOFT 131Page 1 10 – Enumerated Data Types & Procedure Parameters.

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