VB6 pass by value and pass by reference

by

This is a classic gotcha in VB6. It is explained in the VB6 manual. In this code below, VB6 treats the argument as an expression (Test) rather than a variable reference

TestFunction (Test)

In order to pass a reference to the variable either omit the brackets or use the legacy Call statement (which requires brackets)

TestFunction Test
Call TestFunction(Test)

VB6 allows you to pass expressions to ByRef arguments even if the method changes them. Eg you can write

TestFunction (Test + 2)

The compiler creates a temporary copy and passes that by reference. VB.Net uses brackets in a similar way.

You can also get the compiler to create temporary copies if TestFunction takes two arguments like this:

TestFunction (one), (two)

And you can get temporary copies even with Call if you double your brackets, adding an extra unecessary pair:

Call TestFunction((Test))

More Related Contents:

  1. Is there a need to set Objects to Nothing
  2. VBA : save a file with UTF-8 without BOM
  3. Does VBA have Dictionary Structure?
  4. What is the difference between Dim, Global, Public, and Private as Modular Field Access Modifiers?
  5. What does the Call keyword do in VB6?
  6. Difference between Visual Basic 6.0 and VBA
  7. IsDate function returns unexpected results
  8. Getting AD Details based on username
  9. VBScript – How to make program wait until process has finished?
  10. Determine real cause of ODBC failure (error 3146) with ms-access?
  11. VBScript to open a dialog to select a filepath
  12. Alternative IDE for VB6 and VBA [closed]
  13. User Defined Type (UDT) as parameter in public Sub in class module (VB6)
  14. Get reference to additional Inbox
  15. VBA, ADO.Connection and query parameters
  16. Save text file UTF-8 encoded with VBA
  17. Excel column number from column name
  18. How To Speed Up VBA Code
  19. Execute a command in command prompt using excel VBA
  20. Code for looping through all excel files in a specified folder, and pulling data from specific cells
  21. Excel VBA – Combine rows with duplicate values in one cell and merge values in other cell
  22. Load csv file into a VBA array rather than Excel Sheet
  23. MS Access: how to compact current database in VBA
  24. Using colons to put two statements on the same line in Visual Basic [closed]
  25. finding latest file in a folder and opening it (vba access)
  26. reading and writing a csv file using FileSystemObject
  27. Calling regasm without administrative rights for COM interop in Excel VBA
  28. Is there a way for DIR(path) in VBA to handle strings longer than 260?
  29. Call a Unix Script from Excel Vba
  30. Copy an entire worksheet to a new worksheet in Excel 2010

Leave a Comment