Should descendent be able to invoke ancestor's class method?

mtiede · October 15, 2013, 1:44pm

I have this in 3 separate files in one project:

file1:

   type
      TaggedStrings = public class
         public
            class function  DoReplacements( useSettings : Settings; s : String; isLoginWelcomeLabel : boolean ) : String; 
         end;

file2:

   type
      LocalizationBase = public class( TaggedStrings )
         public
          ...
         end;

file3:

   type
        StringProperties = public class( LocalizationBase )
         public
            ...
            class function  GetSubstitutedString( key : String ) : String; override;
            ...
         end;

And this implementation for the StringProperties method:

   class function StringProperties.GetSubstitutedString( key : String ) : String;
      begin
         ...
         result := DoReplacements( GlobalSettings, GlobalSettings.StringLibrary[ key ], false );
         ...
      end;

When I compile it, I get:

Error 9 (PE9) Unknown identifier “DoReplacements”

If I JUST add the keyword “virtual” to the end of the DoReplacements declaration, it compiles fine.

Is this a bug? I would have thought that the descendent class would inherit the ancestor’s class method WITHOUT the virtual keyword and that the virtual would just allow for the overriding in the descendent. I didn’t expect the LACK of a virtual to HIDE the ancestor’s method.

viktoriad · October 16, 2013, 6:38am

Hello,

Sorry but I cannot reproduce your problem here. Could you please send us a simple testcase that shows the problem.

Thanks in advance.

mtiede · October 16, 2013, 12:31pm

On first blush, I can’t reproduce it either. Must have been some other piece I left out. I see I didn’t give the Virtual routine for the one that had the override. But what I gave was an actual copy and paste for what didn’t work. I’ll see if I can get whatever else is there to reproduce it. There is a fair amount of other code, so I’m hesitant to give you the whole thing, but I might do that.

mtiede · October 16, 2013, 12:36pm

Okay, here is one that exhibits the problem.

mtiede · October 16, 2013, 12:37pm

Apparently, the problem happens when the “middle” class has that virtual method.

Patrick · October 16, 2013, 12:51pm

Mark,
with version .1381, I compile your project without any error. Which version of the compiler do you use?
Patrick

mtiede · October 16, 2013, 12:54pm

Yeah, I wondered if it was this older version I am using. Hopefully when I get this project at a good stopping point, I can upgrade. I’ll look up the version as soon as it loads again as it just hung up. It often hangs up after a full build and then compiling just a single project. Hopefully that behavior will go away too.

mtiede · October 16, 2013, 12:55pm

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viktoriad · October 17, 2013, 6:19am

Hello,

I tested your project with latest Oxygene and indeed the problem is not reproduced in it.
Also latest oxygene doesn’t support VS2010, only 2012 and 2013.

Best regards.

mtiede · October 17, 2013, 12:42pm

Thanks for checking. Yeah, I was just talking to my boss in the last couple of days that we should try using 2012 or 2013, but we are in the middle of some major changes so we can’t risk changing at the moment.

mtiede · October 17, 2013, 12:45pm

viktoriad,

I assume you tried REMOVING the virtual in the class in file1 for your test, right?

viktoriad · October 17, 2013, 2:41pm

I’m afraid I didn’t. I only compiled the attached project and the compiling was fine. However I opened the project again and tried to remove virtual, override keywords and recompile it again. Also success.
What could I possibly miss?

mtiede · October 17, 2013, 2:46pm

I assumed you were following along with the discussion. I guess I should have given you a version that failed. It sounds like you removed all virtual and overrides. That would remove the problem. AS I SAID, if you JUST remove the virtual from the class in FILE 1, that produces the error for me.

I’ll recreate it WITH the error in place and re-zip it and re-upload it so that you will be sure to test it in a state that fails for me.

Will upload momentarily.

mtiede · October 17, 2013, 2:49pm

Here it is and it fails to compile for me as it is.

viktoriad · October 18, 2013, 7:03am

Hello,

I retested the project you uploaded and still I have no errors. You have quite old Oxygene version if you are using it with VS2010 so the newer one solved the issue.

Best regards.

mtiede · October 18, 2013, 2:39pm

ok. Thanks.