See, the developers of the Delphi compiler, nothing is impossible.

See, the developers of the Delphi compiler, nothing is impossible.

Originally shared by Maciej Izak

Hi,

I'm pleased to finally announce the additional record operators: Initialize, Finalize.

Download (r33200): http://svn.freepascal.org/svn/fpc/branches/maciej/smart_pointers

"Record management operators aka record constructor/destructor"

They working like low level auto-executed constructor/destructor for records.

===== motivation =====

It can be used for:

-nullable types
-very fast RTTI.TValue implementation
-as replacement for manually called Init/Finit record methods for example like in mORMot for many types.
-auto init/finit for fields of pointer/object type

Additionally, it is base for my further work:

-smart pointers
-ARC objects
-Oxygene mode
-Delphi NextGen mode

===== example begin =====
{$MODE DELPHI}
uses SysUtils;

type
  TFoo = record
  private
    class operator Initialize(var aFoo: TFoo);
    class operator Finalize(var aFoo: TFoo);
  public
    F: Integer;
    S: string;
    P: Pointer;
    C: TObject
  end;

class operator TFoo.Initialize(var aFoo: TFoo);
begin
  aFoo.F := 10;
  aFoo.S := 'FPC rulezzz';
  aFoo.P := nil;
  aFoo.C := nil;
end;

class operator TFoo.Finalize(var aFoo: TFoo);
begin
  if aFoo.S = 'Delphi rulezzz' then
    raise Exception.Create('Trololo');
  FreeMem(aFoo.P);
  aFoo.C.Free;
end;

procedure Foo;
var
  f: TFoo;
begin
  WriteLn(f.F); // output: 10
  WriteLn(f.S); // output: FPC rulezzz
  WriteLn(f.P = nil); // output: true
  WriteLn(f.C = nil); // output: true
end;

begin
  Foo;
end.
===== example end=====

===== more info =====

When Initialize of Finalize is used, record is treated as managed record (similar to record containg string, interface or dynamic array).

It works correctly in all possible ways, works for: 

* New
* Dispose
* Initialize
* Finalize
* InitializeArray
* FinalizeArray
* global variables
* local variables
* for fields inside: records, objects, classes

===== additional gain =====

Speed of dynamically created instances for records increased. For now is used always init table instead of rtti table:

type
  TBar = record
    f1,f2,f3,f4,f5,f6,f7,f8,f9: byte;
    s: string;
  end;

previously:

  GetMem(PB, SizeOf(TBar));
  InitializeArray(PB, TypeInfo(TBar), 1); // FPC_INITIALIZE was executed 10 times

now:

  GetMem(PB, SizeOf(TBar));
  InitializeArray(PB, TypeInfo(TBar), 1); // FPC_INITIALIZE is executed just once
 

===== more examples =====

http://svn.freepascal.org/cgi-bin/viewvc.cgi/branches/maciej/smart_pointers/tests/test/toperator90.pp?view=co&revision=33200&content-type=text%2Fplain&pathrev=33200

http://svn.freepascal.org/cgi-bin/viewvc.cgi/branches/maciej/smart_pointers/tests/test/toperator91.pp?view=co&revision=33200&content-type=text%2Fplain&pathrev=33200

http://svn.freepascal.org/cgi-bin/viewvc.cgi/branches/maciej/smart_pointers/tests/test/toperator92.pp?view=co&content-type=text%2Fplain&pathrev=33200

http://svn.freepascal.org/cgi-bin/viewvc.cgi/branches/maciej/smart_pointers/tests/test/toperator93.pp?view=co&content-type=text%2Fplain&pathrev=33200

===== more details from commit message =====

http://svn.freepascal.org/cgi-bin/viewvc.cgi/branches/maciej/smart_pointers/?view=log&sortby=date&pathrev=33200
http://svn.freepascal.org/svn/fpc/branches/maciej/smart_pointers