From VBA to Delphi conversion (Optional arguments issue)

Question posted 2016 · +2 upvotes

At the moment I’m converting a project written in VBA to Delphi and have stumbled upon a problem with converting some Subs with Optional arguments. Say, there is a Sub declaration (just an example, actual Subs have up to 10 optional parameters):

Sub SetMark
    (x0 As Double, y0 As Double, 
     Optional TextOffset As Integer =5,
     Optional TextBefore As String = "",
     Optional Text As String = "",
     Optional TextAfter As String = "mm",
     Optional Color As String = "FFFFFF",
     Optional ArrowPresent As Boolean = True)

That Sub subsequently can be called like this:

    Call SetMark (15, 100,,,"135")
    Call SetMark (100, 100, 8,, "My text here..", "")
    'a lot of calls here

The Optional arguments are very flexible here, you can omit any of them, and you can assign a value to any of them as well. Unlike in Delphi.

Procedure SetMark
    (x0: real; y0: real, 
            TextOffset: Integer =5;
     TextBefore: ShortString = '';
     Text: ShortString = '';
     TextAfter: ShortString = 'mm';
     Color: ShortString = 'FFFFFF';
     ArrowPresent: Boolean = True);

It seems you cannot just make a copy of VBA call:

SetMark (15, 100,,,'135');// error here 

So, the question is: is there any way to convert that Subs to Delphi procedures keeping the same flexibility in parameters? My first idea was to use default parameters, but it doesn’t work. As for now it seems in Delphi I will have to pass all the parameters in the list with their values directly but that means a lot of work for reviewing and proper porting of VBA calls.

Any ideas?