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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for November 6th, 2018

Delphi: updating a (potentially non-existing) item in a generic TDictionary: use ExtractPair. Except in Delphi 2010/XE.

Posted by jpluimers on 2018/11/06

“Documented” in Delphi 2010, [Archive.is] Generics.Collections.TDictionary.ExtractPair – RAD Studio VCL Reference, and functioning bug-free since Delphi XE2, but still hardly documented, [Archive.is] System.Generics.Collections.TDictionary.ExtractPair – XE2 API Documentation is the easiest way to get a value out of a dictionary and updating it, even if it does not exist.

ExtractPair extracts the TPair<TKey, TValue> if it exists (and removes it from the dictionary) or returns a Default initialised one if not. Though Default is still not documented, you can find an example at [WayBack] How to properly free records that contain various types in Delphi at once? – Stack Overflow.

Example code for ExtractPair:

  FEceptionDictionary := TDictionary<TExceptionKey, Integer>.Create();

...

var
  ExceptionCountPair: TPair<TExceptionKey,Integer>;
begin
  TMonitor.Enter(FEceptionDictionary);
  try
    ExceptionCountPair := FEceptionDictionary.ExtractPair(ExceptObj.ClassType); // extracts and removed from dictionary!
    FEceptionDictionary.Add(ExceptionCountPair.Key, ExceptionCountPair.Value + 1); // use Value as count
  finally
    TMonitor.Exit(FEceptionDictionary);
  end;
end;

In Delphi 2010 and XE it was buggy (see [WayBack] QualityCentral 80947: TDictionary.ExtractPair Fails and creates memory leak via [WayBack] generics – Delphi TPair Exception – Stack Overflow), but since then it works fine, and now is properly documented:

[WayBack] System.Generics.Collections.TDictionary.ExtractPair – RAD Studio API Documentation

Returns the TPair<TKey,TValue> pair with the specified Key and [WayBackremoves the returned pair from a dictionary.

If the dictionary does not contain the specified Key, the returned pair contains a default TValue.

–jeroen

Posted in Delphi, Development, Software Development | 5 Comments »

Validating a nested XML element with an empty namespace using XSD – Stack Overflow

Posted by jpluimers on 2018/11/06

In a quest for making Delphi Group Project XML files (with extension .groupproj) validate with XSD, I had to find out about [WayBackValidating a nested XML element with an empty namespace using XSD – Stack Overflow.

I needed the XSD so I could import it in Delphi in order to write a good .groupproj file generator.

They are here:

And some more background posts are here:

–jeren

Posted in Delphi, Development, Software Development, XML, XML/XSD, XSD | 1 Comment »

Some Computerphile videos starring Professor Brian Kernighan

Posted by jpluimers on 2018/11/06

Most you probably know [WayBackProfessor Brian Kernighan or the YouTube channel Computerphile (sister channel of Numberphile).

He stars in about half a dozen of their videos giving a nice insight in his contributions to the field and how well he can explain things.

Full videos are below; these are the titles:

BTW: If you like those youtube channels, check out [WayBackBrady Haran – Video Journalist who produces similar channels as well.

–jeroen

Read the rest of this entry »

Posted in *nix, Awk, C, Development, Power User, Scripting, Software Development | Leave a Comment »

 
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