Records

[Kas Ob.]

Zitat von Der schöne Günther:

Ich finde es zwar schon legitim, dass Delphi die Record-Felder nicht implizit initialisiert, ist ja eine Performance-Sache.

Can't agree more, i am fan of performance.

Zitat von Phoenix:

Zitat von Der schöne Günther:

Ich finde es zwar schon legitim, dass Delphi die Record-Felder nicht implizit initialisiert, ist ja eine Performance-Sache.

Korrekt. Das aber zusätzlich anzubieten, als Option irgendwo alà "Ich weiß, es ist langsamer, aber ist auch sicherer, also mach an" wäre trotzdem nice.

Oder eben allein schon der Check als Compiler Hint oder gar Warning: "Hey, hier arbeitest Du mit nicht initialisierten Werten!", die Du dann beachten kannst oder aber im Stil von "Ich bin ein Software-Ingenieur, ich weiß, was ich tue", an der Stelle bewusst deaktivieren kannst, das wäre auch nett. Und ehrlich gesagt ist sowas inzwischen ja auch State-of-the-art.

Can't agree more, i am fan of more concrete and double checked code by the compiler and me, also with short and beautiful readable code, State-of-the-art is progress and always helpful.

Where is the problem, it is in taking the whole thing in one way, one direction, and denying other approaches, i am always was (and still) with more tools and options to work and use and realize what in my head.

Is there a way to have both without breaking backward compatibility, yes there is, but it needs open minds, sorry for the last phrase, because i already suggest similar or the same thing in other forum, and no one commented or did they, i can't remember.

Anyway, how about adding new directive or modifier for the variables in the var section and for the inline variables, something like

Code:

Procedure Test;
var
  MyRec: TMyRecord; Init;

and that it, also we can have a directive to tell the compiler to handle every record forward in this unit to Init to default, here comes simple initialization like filling with 0 or calling TMyRecord.Init;

Another example , which i really wish we had in Pascal/Delphi:

Code:

procedure CompareAndAddList(TargetList, SrcList1, SrcList2 : TStringList);
begin
......  // irrelevant 
end;

Procedure Test;
var
  List1, List2, List3 :TStringList; Auto;
begin
  List1.LoadFromFile....
  List2.GetDataFromSomewhere....
  CompareAndAddList(List1, List2, List3);
end;

No .Create, No .Free and definitely no that ugly nested try..finally, the compiler will insert the try..finally and call the constructor and destructor for each class, and we left with concrete will defined code, error free, and beautiful very beautiful and readable code, not breaking any thing.
In my opinion %99 of try..finally is just for calling Free, well some prefer here unnecessary FreeAndNil, but also doable.


are these approaches viable ? , yes they are since the compiler does in fact insert try..finally automatically for managed types, then why it can't add it for any type, on other hand for non managed types, compiler as i understand has inline variables now, so this line "var i := 0 ;", well how is that hard to handle the variables in var sections as inline and but insert them after "begin"
So technically it is there, just need to connect the dots, it is happening with all the VCL components, they are created and free without your code interaction, so have a public, private or protected var as TMyClass in Parent class declared as " CL: TMyClass; auto;" and the compiler will add create and free call in the parent constructor and destructor, how this is far away from using a string in that parent class ?!!

Hope someone will read this and request such thing, so Embarcadero after finishing their cosmic ships (eg. LSP so we can live on Mars happily ever after), will have time to make some progress on the IDE, compiler, and may be the Lnaguage in this case.

Sorry for ranting, and sorry more if this away from topic.

[Edelfix]

Wie ist es mit so einer Lösung? Spricht irgend etwas dagegen?

Delphi-Quellcode:

class operator TMyRecord.Initialize(out Dest: TMyRecord);
var
  LContext: TRttiContext;  // Uses System.Rtti
  LType: TRttiType;
  LRecord: TRttiRecordType;
  LField: TRttiField;
begin
  LContext := TRttiContext.Create;
  try
    LType := LContext.GetType(TypeInfo(TMyRecord));
    if LType.IsRecord then
    begin
      LRecord := LType.AsRecord;
      //--
      for LField in LRecord.GetFields do
      begin
        if (LField.FieldType.TypeKind=tkEnumeration) then
        begin
          if LField.FieldType.Handle = TypeInfo(Boolean) then
            LField.SetValue(@Dest, false)
        end else
        if (LField.FieldType.TypeKind=tkUString) then
          LField.SetValue(@Dest, '')
        else
        if (LField.FieldType.TypeKind=tkInteger) then
          LField.SetValue(@Dest, 0)
        else
        if (LField.FieldType.TypeKind=tkFloat) then
          LField.SetValue(@Dest, 0);
      end;
    end;
  finally
   LContext.Free;
  end;
  //Dest.Value := 10;
  //Dest := Default(TMyRecord);
end;

[dummzeuch]

Zitat von Edelfix:

Wie ist es mit so einer Lösung? Spricht irgend etwas dagegen?

Delphi-Quellcode:

        if (LField.FieldType.TypeKind=tkUString) then
          LField.SetValue(@Dest, '')
        else

Stringtypen werden bereits automatisch mit einem Leerstring initialisiert.

Ansonsten spricht nichts dagegen, allerdings fehlen viele weitere Datentypen, insbesondere Unter-Records.

Und es funktioniert natürlich nur, wenn man die Erweiterte RTTI nicht abschaltet (wenn ich mich recht erinnere, ist das ein Compilerschalter).

[Mavarik]

Zitat von Edelfix:

Wie macht ihr das?

Beispiel Initialisierung:

Delphi-Quellcode:

unit Unit1;

interface

type
  TRQRec = record
    isActiv: Boolean;
  end;

implementation

procedure Test1;
var
  RQRec: TRQRec;
begin
  Fillchar(RQRec,Sizeof(RQRec),#0);

  if RQRec.isActiv then // es ist manchmal true
  begin
    // do amasing things
  end;
end;

end.

Beispiel Record wird an eine Procedure übergeben und ich will testen ob es initialisiert wurde:

Delphi-Quellcode:

unit Unit1;

interface

type
  TRQRec = record
    Data : integer;
    isActiv: String;
    Constructor Create(aData : Integer);
  end;

implementation

procedure Test1;
var
  RQRec: TRQRec;
begin
  if RQRec.isActiv = '' then
    RQRec := TQRRec.Create(42);
end;

Constructor TRQRec.Create(aData : Integer);
begin
  Data := aData;
  isActiv := '*';
end;

end.

[mytbo]

Zitat von Kas Ob.:

Code:

Procedure Test;
var
  MyRec: TMyRecord; Init;

and that it, also we can have a directive to tell the compiler to handle every record forward in this unit to Init to default, here comes simple initialization like filling with 0 or calling TMyRecord.Init;

In newer Delphi versions you can already do a lot. Defined with a few lines and clearer for me:

Delphi-Quellcode:

type
  TTestRec = record
    Name: String;
    Count: Integer;
    Address: array of record
      Street: String;
      ZIPCode: Integer;
    end;
  public
    function AddAddress(const pmcStreet: String; pmZIPCode: Integer): Integer;
    procedure Init;
    procedure Clear;
  end;

function TTestRec.AddAddress(const pmcStreet: String; pmZIPCode: Integer): Integer;
begin
  Result := Length(Address);
  SetLength(Address, Result + 1);
  with Address[Result] do
  begin
    Street := pmcStreet;
    ZIPCode := pmZIPCode;
  end;
end;

procedure TTestRec.Init;
begin
  FillChar(Self, SizeOf(Self), 0);
end;

procedure TTestRec.Clear;
begin
  Finalize(Self);
  Init;
end;

Or functions are outsourced to a record helper. Use it like this:

Delphi-Quellcode:

var
  rec: TTestRec;
begin
  rec.Init;
  ShowMessage(rec.Count.ToString);
  rec.AddAddress('Paddington', 123);
  ShowMessage(rec.Address[0].ZIPCode.ToString);
  rec.Clear;
  ShowMessage(Length(rec.Address).ToString);

Zitat von Kas Ob.:

... No .Free and definitely no that ugly nested try..finally, ...

There is something similar (not the same) in mORMot. Used very carefully, it can be helpful:

Delphi-Quellcode:

var
  sList1, sList2: TStringList;
  oList1, oList2: TObjectList;
begin
  with TAutoFree.One(sList1, TStringList.Create) do
  begin
    sList1.Add('Test');
    Another(oList1, TObjectList.Create);
    oList1.Add(TObject.Create);
  end;

  with TAutoFree.Several([
    @sList2, TStringList.Create,
    @oList2, TObjectList.Create]) do
  begin
    sList2.Add('Test');
    oList2.Add(TObject.Create);
  end;
end;

I would like to see the NameOf function much more urgently. Although it is highly voted, we hear nothing about its realization.

With best regards
Thomas

[himitsu]

Zitat von Edelfix:

Delphi-Quellcode:

class operator TMyRecord.Initialize(out Dest: TMyRecord);
begin
  //Dest.Value := 10;
  Dest := Default(TMyRecord);
end;

Ich hätte hier eine Endlosschleife erwartet.

Default() müsste doch den Record initialisieren, also auch den ClassConstructor aufrufen.

[Kas Ob.]

Zitat von mytbo:

Zitat von Kas Ob.:

Code:

Procedure Test;
var
  MyRec: TMyRecord; Init;

and that it, also we can have a directive to tell the compiler to handle every record forward in this unit to Init to default, here comes simple initialization like filling with 0 or calling TMyRecord.Init;

In newer Delphi versions you can already do a lot. Defined with a few lines and clearer for me:

Delphi-Quellcode:

type
  TTestRec = record
    Name: String;
    Count: Integer;
    Address: array of record
      Street: String;
      ZIPCode: Integer;
    end;
  public
    function AddAddress(const pmcStreet: String; pmZIPCode: Integer): Integer;
    procedure Init;
    procedure Clear;
  end;

function TTestRec.AddAddress(const pmcStreet: String; pmZIPCode: Integer): Integer;
begin
  Result := Length(Address);
  SetLength(Address, Result + 1);
  with Address[Result] do
  begin
    Street := pmcStreet;
    ZIPCode := pmZIPCode;
  end;
end;

procedure TTestRec.Init;
begin
  FillChar(Self, SizeOf(Self), 0);
end;

procedure TTestRec.Clear;
begin
  Finalize(Self);
  Init;
end;

Or functions are outsourced to a record helper. Use it like this:

Delphi-Quellcode:

var
  rec: TTestRec;
begin
  rec.Init;
  ShowMessage(rec.Count.ToString);
  rec.AddAddress('Paddington', 123);
  ShowMessage(rec.Address[0].ZIPCode.ToString);
  rec.Clear;
  ShowMessage(Length(rec.Address).ToString);

Zitat von Kas Ob.:

... No .Free and definitely no that ugly nested try..finally, ...

There is something similar (not the same) in mORMot. Used very carefully, it can be helpful:

Delphi-Quellcode:

var
  sList1, sList2: TStringList;
  oList1, oList2: TObjectList;
begin
  with TAutoFree.One(sList1, TStringList.Create) do
  begin
    sList1.Add('Test');
    Another(oList1, TObjectList.Create);
    oList1.Add(TObject.Create);
  end;

  with TAutoFree.Several([
    @sList2, TStringList.Create,
    @oList2, TObjectList.Create]) do
  begin
    sList2.Add('Test');
    oList2.Add(TObject.Create);
  end;
end;

I would like to see the NameOf function much more urgently. Although it is highly voted, we hear nothing about its realization.

With best regards
Thomas

Nice points.

I am familiar with the above, so let me clear more on that.

1) Yes adding Init as record constructor to each and every record is doable, but, do i really want to add such code every where, or revert to helpers and lose the ability to use another helper in more constructive way for such small functionality, anyway it is not about record per se, see the suggested Init could be with anything like signed or unsigned integers, counters, index, float, chars, Booleans, short strings, array [fixedsize] of (bytes, chars, ), .... etc... and most critical my own types, simply for every type that can have value, if 0 is possible value then fill it, otherwise use the smallest value or the first defined like these, they could have default value and i don't need to worry about

Code:

type 
  Suit = (Club, Diamond, Heart, Spade); 
  Size = (Small = 5, Medium = 10, Large = Small + Medium); 
  SomeNumbers = -128..127;
  Caps = 'A'..'Z';
  SomeNum: 1..500;

2) As for TAutoFree from mORMot, i did my share of those as i have my own solution, but still it is not elegant as if done by the compiler.. clear, beautiful and short, also my biggest problem where i count up to 1000 before decide to import and insert an open source library in my project for such small addition, such approach still and will stay error prone and the compiler will not help or warn about memory leak before hand, while such Auto functionality, i can rest assured it is done right.

3) NameOf and IndexOf and TypeOf .. OffsetOf, all of these worth adding not only for Pascal syntax and Delphi RTL but to the assembler too, also the ability to access VMT in easier and way with the ability to distinguish overridden method which will be great too, the point here, these methods are dangerous and defeat of secure coding by override the flow of code dictated by the language itself and curated by compiler, but we have crippled compiler and outdated language, so if Embarcadero can't/wouldn't revise and progress on the front, then we as users should have tools to overcome these ancient obstacles.