{**********************************************************
Simple example of how using pointers

 Author: Didier Cabalé
         'Bellefont'
         31800 Saint-Gaudens, France
         tél: +33 (0)5 61 89 72 92
         e-mail: didier.cabale+delphi@gmail.com
         web-page: http://didier.cabale.free.fr/delphi.htm

***********************************************************}

program Pointers;

{$APPTYPE CONSOLE}

{$R *.res}

uses
   System.Types // TIntegerDynArray
  , System.Generics.Collections // PObject
  , System.SysUtils  // IntToStr()
  ;

type

  TStatIntArray = Array[0..1] of Integer;
  PStatIntArray = ^TStatIntArray;

  TStatCharArray = Array[0..5] of Char;
  TRec = record
    aField: TStatCharArray;
  end;
  PRec = ^TRec;

const
  cI: integer = 100;
  cS: ShortString = 'didier';
  cStatArray: Array[0..1, 0..1] of Integer = ((1, 2), (3, 4));
  aRec: TRec = (aField: 'cabalé');

var
  O, O2: TObject;
  PointersArr: Array of Pointer;
  P: Pointer;
  IntArray: TIntegerDynArray;  // IntegerArray is static
  i: Integer;

begin
  try
    { TODO -oUser -cConsole Main : Insert code here }
    O := TObject.Create;
    try

      SetLength(PointersArr, 6);
      PointersArr[0] := @cI;
      PointersArr[1] := Addr(cS); // Addr equiv @
      i := Integer(PointersArr[1]);
      PointersArr[2] := @cStatArray[0, 0];
      SetLength(IntArray, 2);
      IntArray[0] := 11;
      IntArray[1] := 12;
      PointersArr[3] := @IntArray[0];
      PointersArr[4] := @aRec;
      PointersArr[5] := @O;

      Writeln('----------------');
      Writeln('pointer values:');
      for P in PointersArr do
        Writeln(Integer(P));

      Writeln('----------------');
      Writeln('data at pointers address:');
      Writeln('cI: ', PInteger(PointersArr[0])^);
      Writeln('cS: ', PShortString(i)^); // integer can be typecasted
      Writeln('cStatArray value: '+ Format('(%d, %d)', [PStatIntArray(PointersArr[2])^[0], PStatIntArray(PointersArr[2])^[1]]));
      Writeln('aDynArray value: '+ Format('(%d, %d)', [PStatIntArray(PointersArr[3])^[0], PStatIntArray(PointersArr[3])^[1]]));
      Writeln('aRec.aField: '+ PRec(PointersArr[4])^.aField);
      Writeln('O class: '+ PObject(PointersArr[5])^.ClassName);

      Writeln('----------------');
      Writeln('Type instance <-> Pointers');
      Writeln('O.ClassName: ', O.ClassName);
      PointersArr[5] := @O;
      Writeln(Format('PointersArr[5] Value: %d; PointersArr[5] reference: %s', [Integer(PointersArr[5]), PObject(PointersArr[5])^.ClassName]));
      O2 := TObject(PointersArr[5]^);
      Writeln('proof of back reference: O2.ClassName: ', O2.ClassName);

    finally
      O.Free;
    end;
    Readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.