Bypass extends method

Targets Web
1

Hi!

I’m creating a module to help me to start my migration from my xojo 2018 web project to 2021 version.

so, i’m “extending” some object methods. for example:

on 2018 project, i did:

Public Sub RemoveAllRows(extends lbx as WebListBox)
lbx.DeleteAllRows
End Sub

So i can change all my 2018’s bx.DeleteAllRows to lbx.RemoveAllRows
Then, when i open on my 2021 xojo ide, all will be ready!

But, how can i use or ignore this method depending on xojo’s version?
How can i use the actual “lbx.RemoveAllRows” for the 2021 version, instead of calling my own method?

Another example…

Public Sub MessageBox(myMessage as string)
#if XojoVersionString=“2018r1.1” then
MsgBox(myMessage)
else
MessageBox(myMessage)
#endif
End Sub

How to use MY METHOD for 2018 version, and XOJO’S METHOD for 2021 version?
if i use my messagebox with an “else” to call xojo MessageBox, it’ll give me a stack overflow

Thank you all!

2

When you use the new Xojo version you delete the module from the project.

3

yep, but i want to do this gradually, so i want to run on 2018, and just check if it’s all ok on 2021.

i want to execute on 2021, and during the tests, i’ll implement the “upgrades” on my module. then back to 2018, check, go to 2021, check…

4

Compatibility Flags

you can indicate something should only be available for versions prior to 2019r2 by checking the API 1 flag.

Note: Compatibility flags are shown on the Advanced tab of the Inspector.

5

You should be able to use the explicit namespace to solve this issue, but I’m not sure if that’s possible with some calls.

E.g. something like this:

Public Sub MessageBox(myMessage as string)
#if XojoVersionString=“2018r1.1” then
  MsgBox(myMessage)
else
  Xojo.MessageBox(myMessage)  // call the built-in framework version, rather than this override method
#endif
End Sub

However, the documentation does not say whether this is possible: https://documentation.xojo.com/api/language/me.htmlssageBox

2 Likes
6

there is no copatibility flags on 2018…

:frowning:

7

for messageBox worked just fine!

and for this one?

Public Function CellValueAt(extends lbx as WebListBox, Row as integer, Column as integer) as string
#if XojoVersionString=“2018r1.1” then
return lbx.Cell(row,column)
#else
return Xojo…???
#endif
End Function

8

@Alexandre_Cunha please remember to use the Preformated Text button for source code (it looks like this in the forum): image so your code will be nicely formatted.

I’m not sure what you want to do is possible - the documenation says:

Methods declared in this way are sometimes called “class extension methods” even though they are not actually part of a class. You can use Extends only for methods in a module. Extends cannot be used to override another method. Extension methods are not virtual, since they are not part of a class.

https://documentation.xojo.com/api/language/extends.html

Edit: indeed, if you try to Extend an existing class method, it fails:

Public Function Len(extends s as String) as integer
  return s.Len
End Function

image