GAMBAS-BOOK 3.19.5

The syntax for this control structure may surprise you with its variety - but it can be implemented quickly in practical use:

SELECT [ CASE ] Expression 

  [ CASE [ Expression ] [ TO Expression #2 ] [ , ... ] 
    ... ] 

  [ CASE [ Expression ] [ TO Expression #2 ] [ , ... ] 
    ... ] 

  [ CASE LIKE Expression [ , ... ] 
    ... ] 

  [ { CASE ELSE | DEFAULT } 
    ... ] 

END SELECT

• The notation from Case to Select is optional.
• An expression is specified as a selector and then the code is executed in the appropriate case statement.
• If no case expression matches the selector, the system executes the default or case Else statement (if available).
• A case statement is a single value, a comma-separated list of single values, or an interval of values separated by the To keyword.
• You can also make case distinctions with the Like operator.
• In selected cases, the control structure is Select.. Case.. End_Select of a nested control structure If… Then… Else_If_End_If - with the same effect - is preferable, because it gives the source code an easily readable structure.

The examples mainly show source code excerpts and are commented on briefly.

Example 1

The selection is made for different (number ranges) with different selectors:

Public Sub GetInformation(iNumber As Integer)  
  Select Case iNumber
    Case 0 
      Print "Selection = 0"
    Case 1 To 2
      Print "Selection 1 or 2"
    Case 3 To 5, 7 To 9
      Print "Choose between 2-5 or 7-9"
    Case 6
       Print "Selection = 6"
    Case Else
      Print "Selection not in range 0-9"
    End Select
End
 
' Public Sub GetInformation(iNumber As Integer) 
'   Select CStr(iNumber)
'     Case "0" 
'       Print "Selection 0"
'     Case Like "[1-2]" 
'       Print "Selection 1 or 2"
'     Case Like "[3-57-9]" ' Case Like "[345789]" 
'       Print "Choose between 3-5 or 7-9"
'      Case "6" 
'       Print "Selection 6"
'     Case Else
'       Print "Selection not in range 0-9"
'     End Select' 
' End 

A numerical value (0 and 6), a numerical range 1-2 or a list of two numerical ranges 3-5 and 7-9 are used as selectors. The commented out source code uses the Like operator for the selectors.

With this source code after clicking on the corresponding button

Public Sub btnSelectedRange_Click()
  GetInformation(0)
  GetInformation(2)
  GetInformation(8)
  GetInformation(6)
  GetInformation(13)
End ' btnSelectedRange_Click()

the following lines in the console of the IDE:

Selection = 0
Selection 1 or 2
Choice between 2-5 or 7-9
Selection = 6
Selection not in range 0-9

Example 2

First, specify an If..Then..Else_If_End_If control structure for three alternative cases:

  For iNumber = 0 To xmlNode.Children.Count - 1 
 
    sBuffer = xmlNode.Children[iNumber].Name
 
    If sBuffer = "title" Then 
       sTitle = xmlNode.Children[iNumber].Value 
    Else If sBuffer = "link" Then 
       sItemLink = xmlNode.Children[iNumber].Value 
    Else If sBuffer = "description" Then 
       sDescription = xmlNode.Children[iNumber].Value 
    Endif
 
  Next 

and then the implementation into an adequate Select.Case..End_Select control structure:

  For iNumber = 0 To xmlNode.Children.Count - 1 
 
    sBuffer = xmlNode.Children[iNumber].Name
 
    Select Case sBuffer 
      Case "title" 
        sTitle = xmlNode.Children[iNumber].Value 
      Case "link" 
        sItemLink = xmlNode.Children[iNumber].Value 
      Case "description" 
        sDescription = xmlNode.Children[iNumber].Value 
    End Select
 
  Next

Example 3

PUBLIC SUB Form_KeyPress() 
 
  IF Key.Control 
     SELECT CASE Workspace1.Children.Find(Workspace1.ActiveWindow) 
       CASE 0 TO Workspace1.Children.Count - 2 
         Workspace1.ActiveWindow = 
         Workspace1.Children[Workspace1.Children.Find(Workspace1.ActiveWindow) + 1] 
       CASE Workspace1.Children.Count - 1 
         Workspace1.ActiveWindow = Workspace1.Children[0] 
       CASE ELSE 
       ' Alternative ...
     END SELECT 
  ENDIF 
 
END

The first case checks a list of values. There is no alternative selection for 'CASE ELSE' - but it is planned!

Example 4

Public Sub GetStatus(sStatus As String)
  Select sStatus
    Case Like "[+Pp]*"
      Message.Info(IIf(sStatus Begins "+", "Status: positiv", "Status: " & sStatus))
    Case Like "[-Nn]*"
      If sStatus Begins "-" Then sStatus = "negativ"
      Message.Info("Status: " & sStatus)
    Default
      Message.Error("Der Status konnte NICHT ermittelt werden!")
  End Select
End ' GetStatus(sStatus As String)

• The select in the second line is not followed by a case here, because its specification is optional.
• The case differentiations are implemented in the two regular cases using the Like operator (? chapter 8.3.3 LIKE).
• The preparation of the messages is done in different ways.
• The error message is only displayed if neither of the two regular cases applies.

Calling GetStatus (“Status ok”) in the following procedure

Public Sub btnSelect_Click()
  GetStatus("Status ok")
End ' btnSelect_Click()