Computer Programming Concepts and Visual Basic David I. Schneider

88 Computer Programming Concepts and Visual Basic
FirstName = Left(nom, firstSpace - 1)
End Function
The value of each of the preceding functions is assigned by a statement of the form
FunctionName = expression. The variables t and nom appearing in the preceding functions
are parameters. They can be replaced with any variable of the same type without affecting the
function definition. For instance, the function FtoC could have been defined as
Private Function FtoC(temp As Single) As Single
‘Convert Fahrenheit temperature to Celsius
FtoC = (5 / 9) * (temp - 32)
End Function
Like Sub procedures, Function procedures can be created from a code window with Alt/T/P.
The only difference is that the circle next to the word Function should be selected. After the
name is typed and the OK button is clicked, the lines Private Function FunctionName( ) and
End Function will be placed automatically (separated by a blank line) in the code window.
EXAMPLE 1
The following program uses the function FtoC.
Private Sub cmdConvert_Click()
picTempC.Cls
picTempC.Print FtoC(Val(txtTempF.Text))
End Sub
Private Function FtoC(t As Single) As Single
‘Convert Fahrenheit temperature to Celsius
FtoC = (5 / 9) * (t - 32)
End Function
Object Property Setting
frm4_3_1 Caption Convert Fahrenheit to
Celsius
lblTempF Caption Temperature
(Fahrenheit)
txtTempF Text (blank)
cmdConvert Caption Convert to Celsius
lblTempC Caption Temperature (Celsius)
picTempC
[Run, type 212 into the text box, and then click the command button.]
EXAMPLE 2
The following program uses the function FirstName.
Object Property Setting
frm4_3_2 Caption Extract First Name
lblName Caption Name
txtFullName Text (blank)
cmdDetermine Caption Determine First Name
picFirstName