COMM 1A Application Building

1

• COMM 1A Application Building
• Unit 8

2
Introduction

• Objectives for the Session
• To be aware of the need for re-naming objects and
  a common Naming Convention
• To be able to understand the nature of Wizard
  Code
• To understand the need for Housekeeping
• To understand the syntax and use of the If
  construct
• To understand the syntax and use of the Select
  Case construct

3
Naming Conventions

• Objects and variables must have a unique name
• Default names
• Rename, as a minimum, all objects that are
  influenced by code
• Do it before you write code!
• Cmd Command Buttons Chk CheckBox
• Lbl Label Cbo ComboBox
• Txt TextBox Lst ListBox
• Opt Option/Radio Button Img Image

4
Wizard Code

• Private Sub CmdOpenSplitting_Click()
• On Error GoTo Err_CmdOpenSplitting_Click
• Dim stDocName As String
• Dim stLinkCriteria As String
• stDocName "Splitting lines of code"
• DoCmd.OpenForm stDocName, , , stLinkCriteria
• Exit_CmdOpenSplitting_Click
• Exit Sub
• Err_CmdOpenSplitting_Click
• MsgBox Err.Description
• Resume Exit_CmdOpenSplitting_Click
• End Sub

5
Housekeeping

• Delete an object with code and the code remains
• Re-create the object and you get duplicate code
• Tidy up as you go

6
Control Constructs

• Control the flow of a program
• Sequence
• Each line of code is performed in order
• Selection
• One block of code is performed rather than
  another
• Iteration
• A block of code is repeated a number of times

7
The If Statement

• Syntax
• If condition Then statements Else else
  statements
• Example
• txtInput.SetFocus
• If txtInput.Text Fred Then txtInput.BackColor
  RGB(100, 150, 175)

8
The If Statement

• Syntax
• If condition Then
• statements
• ElseIf condition-n Then
• elseif statements
• Else
• else statements
• End If

• Example
• txtInput1.Text.SetFocus
• If txtInput1.Text Fred Then
• txtOutput.SetFocus
• txtOutput.Text Hello Fred
• ElseIf txtInput1.Text Peter Then
• txtOutput.SetFocus
• txtOutput.Text Hello Peter
• Else
• txtOutput.SetFocus
• txtOutput.Text Hello whoever you are
• End If

9
The Select Case Statement

• Syntax
• Select Case testexpressionCase expressionlist-n
  statements-n ...Case Else else statements
• End Select
• Example
• txtThree.SetFocus
• Select Case txtThree.Text
• Case "1"
• txtOutput.SetFocus
• txtOutput.Text "You typed 1"
• Case "2"
• txtOutput.SetFocus
• txtOutput.Text "You typed 2"
• Case Else
• txtOutput.SetFocus
• txtOutput.text What you have typed in not 1
  or 2
• End Select

10
Summary

• Get into the habit of re-naming objects
• Wizard code works in exactly the same way as code
  you create and can be modified in the same way,
  if necessary
• Housekeeping makes it easier for you and others
  to understand your system design
• Selection is a logical test of truth and,
  regardless of the choice of construct, code will
  only be run if the test is true