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Author Topic: [SOLVED] Free dynamic array of objects  (Read 1060 times)

pcurtis

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[SOLVED] Free dynamic array of objects
« on: May 26, 2021, 10:48:45 am »
Consider this

Code: Pascal  [Select][+][-]
  1. type
  2.   TMyType = record
  3.     abc : Integer;
  4.     def : TStringList;
  5.   end;
  6.  
  7. var
  8.   MyArray : array of TMyType;
  9.  
  10. implementation
  11.  
  12. procedure xxx;
  13. var
  14.   iTEMP : Integer;
  15. begin
  16.   SetLength(MyArray, 1000);
  17.  
  18.   for iTEMP := 0 to 999 do
  19.     begin
  20.       MyArray[iTEMP].abc := 5;
  21.       MyArray[iTEMP].def := TStringList.Create;
  22.     end;
  23. end;
  24.  

How do I free all the objects in the array?.
Is  SetLength(MyArray, 0); enough?
« Last Edit: May 26, 2021, 12:23:23 pm by pcurtis »
Windows 10
Laz 2.0.10
FPC 3.2.0

lucamar

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Re: Free dynamic array of objects
« Reply #1 on: May 26, 2021, 11:02:01 am »
No, before that you'll have to traverse the array freeing the string lists:

Code: Pascal  [Select][+][-]
  1.   for i := Low(MyArray) to High(MyArray) do
  2.       MyArray[i].def.Free;
  3.   SetLength(MyArray, 0);
« Last Edit: May 26, 2021, 11:04:22 am by lucamar »
Turbo Pascal 3 CP/M - Amstrad PCW 8256 (512 KB !!!) :P
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marcov

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Re: Free dynamic array of objects
« Reply #2 on: May 26, 2021, 11:04:45 am »
Or use Tobjectlist, which is a class wrapper of an array that can  od it for you

Zvoni

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Re: Free dynamic array of objects
« Reply #3 on: May 26, 2021, 11:10:01 am »
What about advanced records?

From SetLength
https://www.freepascal.org/docs-html/rtl/system/setlength.html
Quote
The elements that fall outside the new length are finalized if the array element is a managed type.

https://wiki.freepascal.org/management_operators
Quote
Each record, even non-managed or empty, that implements any management operators becomes a managed type.
Implementing a Finalize-Operator, freeing the StringList there?
You could even implement an Initialize-Operator to create the StringList there
« Last Edit: May 26, 2021, 11:12:18 am by Zvoni »
One System to rule them all, One IDE to find them,
One Code to bring them all, and to the Framework bind them,
in the Land of Redmond, where the Windows lie
---------------------------------------------------------------------
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Zvoni

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Re: Free dynamic array of objects
« Reply #4 on: May 26, 2021, 11:51:49 am »
Yepp. Works.

Code: Pascal  [Select][+][-]
  1. program Project1;
  2. {$modeswitch advancedrecords}
  3. Uses
  4.   SysUtils, Classes;
  5.  
  6. Type
  7.  
  8.   { TMyType }
  9.  
  10.   TMyType = record
  11.     abc : Integer;
  12.     def : TStringList;
  13.     class operator initialize(var ARec:TMyType);
  14.     class operator finalize(var ARec:TMytype);
  15.   end;
  16.  
  17. Var
  18.   MyArray : array of TMyType;
  19.   i:Integer;
  20.  
  21. { TMyType }
  22.  
  23. class operator TMyType.initialize(var ARec: TMyType);
  24. begin
  25.   ARec.def:=TStringList.Create;
  26.   Writeln('Create StringList');
  27. end;
  28.  
  29. class operator TMyType.finalize(var ARec: TMytype);
  30. begin
  31.   ARec.def.Free;
  32.   WriteLn('Free StringList');
  33. end;
  34.  
  35. begin
  36.   SetLength(MyArray,5);
  37.   For i:=0 To High(MyArray) Do MyArray[i].abc:=i;
  38.   SetLength(MyArray,0);
  39. end.
  40.  
HeapTrc throws no memory-leak

Returns in console.
Create StringList
Create StringList
Create StringList
Create StringList
Create StringList
Free StringList
Free StringList
Free StringList
Free StringList
Free StringList
One System to rule them all, One IDE to find them,
One Code to bring them all, and to the Framework bind them,
in the Land of Redmond, where the Windows lie
---------------------------------------------------------------------
People call me crazy, because i'm jumping out of perfectly fine aircraft

pcurtis

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  • Posts: 634
Re: Free dynamic array of objects
« Reply #5 on: May 26, 2021, 12:22:39 pm »
Thanks all.
Windows 10
Laz 2.0.10
FPC 3.2.0

 

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