我可以直接在stringlist中添加记录作为对象吗？

Question

Currently I am adding object by creating it like:

type    
  TRecord = class
  private
    str: string;
    num: Integer;
  public
    constructor Create;
  end;

...

procedure TForm1.Button2Click(Sender: TObject);
var
  i: Integer;
  rec: TRecord;
  Alist: TStringList;
begin
  Alist := TStringList.create;
  Alist.Clear;
  for i := 0 to 9 do 
  begin
    rec := Trecord.Create; //create instance of class
    rec.str := 'rec' + IntToStr(i);
    rec.num := i * 2;
    Alist.AddObject(IntToStr(i), rec);
  end;
end;

Is this method correct or inefficient ? Or Can I directly add object not by creating it like using record?

type    
  PRec = ^TRec;
  TRec = record
    str: string;
    num: Integer;
  end;

...
var
  rec: TRec;
...

for i := 0 to 9 do 
begin
  //how to write here to have a new record, 
  //can i directly Create record in delphi 7 ?
  rec.str := 'rec' + IntToStr(i);
  rec.num := i*2;
  Alist.AddObject(IntToStr(i), ???); // how to write here?
end;

Or other fast and simple way?

I am using Delphi 7.

Thanks in advance.

Answer 1

The way you're doing it now is fine.

You can't do it with a record without allocating memory when you add a new record to the TStringList.Objects , and you'd have to free it afterwards. You're just as well off using a class as you are now; you have to free the objects before freeing the stringlist. (In more recent versions of Delphi, TStringList has an OwnsObjects property that will auto-free them for you when the stringlist is free'd, but it's not in Delphi 7.)

If you really want to do this with a record, you can:

type    
  PRec = ^TRec;
  TRec = record
    str: string;
    num: Integer;
  end;

var
  rec: PRec;
begin
  for i := 0 to 9 do 
  begin
    System.New(Rec);
    rec.str := 'rec' + IntToStr(i);
    rec.num := i*2;
    Alist.AddObject(IntToStr(i), TObject(Rec)); // how to write here?
  end;
end;

You'll need to use System.Dispose(PRec(AList.Objects[i])) to release the memory before freeing the stringlist. As I said, the way you're doing it now is actually much easier; you don't have to do the typecast when adding to and deleting from the stringlist.

You don't need the AList.Clear , by the way. Since you're creating the stringlist, there can't be anything in it to remove.