TFPSMap.IndexOfData function issue

[zoltanleo]

Hi folks.

For some reason I am trying to use fgl.TFPGMap instead of generics.collection.TDictionary. It seemed to me that the TFPSMap.IndexOfData function was not working properly. Here is an example code that reproduces the issue.

Code: Pascal  [Select][+][-]

1. uses
2.   ...fgl...;
3.  
4. type
5.   TMyTest = specialize TFPGMap<PtrInt,String>;
6. ...
7.   public
8.     property MyTest: TMyTest read FMyTest write SetMyTest;
9.   end;
10. ...
11. var
12.   i: PtrInt = 0;
13. begin
14.   FMyTest:= TMyTest.Create;
15.  
16.  
17.   for i:= 0 to 9 do
18.   MyTest.AddOrSetData(i,Format('string_%d (added as Object: %d)',[Succ(i),i]));;
19.  
20.   ComboBox1.Clear;
21.  
22.   for i:= 0 to Pred(MyTest.Count) do
23.     ComboBox1.Items.Add(MyTest.Data[i]);
24.  
25.   ComboBox1.ItemIndex:= 0;
26.   ComboBox1Change(Sender);
27. ...
28.  
29. procedure TForm1.ComboBox1Change(Sender: TObject);
30. var
31.   k: PtrInt = 0;
32. begin
33.   Label1.Caption:= 'no matches';
34.  
35.   k:= MyTest.IndexOfData(ComboBox1.Items[ComboBox1.ItemIndex]);
36.   if (k > -1) then
37.     Label1.Caption:= 'Key: ' + IntToStr(MyTest.Keys[k]);
38.  
39.   Caption:= IntToStr(MyTest.Count);
40. end;

Plz someone confirm my guess

[marcov]

There are known issues with fgl and ref counted types e.g.

https://gitlab.com/freepascal.org/fpc/source/-/issues/39846

If they are clear to fix, I usually fix them, but in this case I have no idea what the original author meant to do.

I suggest to use TDictionary.

[zoltanleo]

Hi marcov

Thank U for answer

[PascalDragon]

For some reason I am trying to use fgl.TFPGMap instead of generics.collection.TDictionary. It seemed to me that the TFPSMap.IndexOfData function was not working properly. Here is an example code that reproduces the issue.

By default TFPGMap<> does not provide a comparison for the Data type. You need to provide it by assigning the OnDataCompare event:

Code: Pascal  [Select][+][-]

1. { snip }
2. uses
3.   StrUtils;
4.  
5. {$R *.lfm}
6.  
7. { TForm1 }
8.  
9. function CompareStringFunc(const aData1, aData2: String): Integer;
10. begin
11.   Result := AnsiCompareStr(aData1, aData2);
12. end;
13.  
14. procedure TForm1.FormCreate(Sender: TObject);
15. var
16.   i: PtrInt = 0;
17. begin
18.   FMyTest:= TMyTest.Create;
19.   FMyTest.OnDataCompare := @CompareStringFunc;
20. {snip}

Two additional points:

• the corresponding counterpart to the OnCreate event is the OnDestroy event; OnClose might be called multiple times
• your setter for MyTest does not free the original list thus you'll leak memory with every use

There are known issues with fgl and ref counted types e.g.

https://gitlab.com/freepascal.org/fpc/source/-/issues/39846

If they are clear to fix, I usually fix them, but in this case I have no idea what the original author meant to do.

I suggest to use TDictionary.

This has nothing to do with reference counted types.

[AlexTP]

Added this new info to https://wiki.freepascal.org/TFPGMap