Visual Basic and Visual FoxPro Procedures and Functions
VBA
Sub, Function, Exit
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VFP
Procedure, EndProc
Function, Parameters, Return
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Common Syntax Notes
Strictly speaking, a function returns a value and has no other effects whereas
a procedure does have some external effect and returns no value. Visual Basic sticks
to this convention but Visual FoxPro is less strict.
Visual Basic Syntax Notes
VBA Procedure
Visual Basic procedures are declared in a code module with the name of the procedure
followed by the name and type of any parameters it requires:
Public Sub CloseApp()
CloseAllForms True
DropTables
Set gdbs = Nothing
Application.Quit acExit
Exit Sub
A Visual Basic procedure is called by stating the name of the procedure followed by the
names or values of any parameters. In the snippet above, CloseAllForms is a procedure
which is being called with a parameter True. There is an older syntax which uses
Call and puts the parameter(s) into brackets:
Call CloseAllForms (True)
VBA Function
Visual Basic functions are declared in a code module with the name of the function and
the data type it returns together with the names and types of any parameters it requires:
Public Function
GetLatestVersion(strID As String)
As String
GetLatestVersion = DMax(
"Shipped",
"Version",
"ID = '" & strID &
"'")
End Function
The value returned by the function is simply assigned to a variable with the same name
as the function, "GetLatestVersion" in this example. A function is called by assigning
its value to a variable or by using it in an expression where a variable of that data
type would be allowed:
Me.Caption = "Issues for " & GetLatestVersion(mstrID)
Visual FoxPro Syntax Notes
Although FoxPro supports functions and procedures there is no strict distinction between
them. They can exist in a prg file with a Procedure or
Function header as appropriate or they can exist as a
complete prg file with no header. In that situation the entire file acts as though it
were a procedure or function with the same name as the prg file itself.
VFP Procedure
A procedure is declared like this with the parameters listed after a
Lparameters or Parameters
statement:
Procedure MyProc
Lparameters tcParm1, tcParm2
EndProc
Unlike in Visual Basic, there is no need to define the type of the parameters in FoxPro.
A procedure is called like this using Do and
With:
Do MyProc
With "First parameter", "Second parameter"
VFP Function
A FoxPro function is declared like this:
Function MyFunc
Lparameters tcParm1, tcParm2
Return lcAnswer
EndProc
and called like this:
lcValue = MyFunc("First parameter", "Second parameter")
In practice though you can use the function calling syntax on a procedure. If you
examine the return value you'll find that the procedure returns true. There is
however no need have an assignment statement. You can call a procedure as though it were
a function and just throw the return value away:
MyProc("First parameter", "Second parameter")
VFP Method
A VFP method is just a function which is declared inside a
Define Class block.
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