Is it memory safe to provide an object as a function result?

manpreet Best Answer 2 years ago

Here I provide simple piece of code.

function GetStringList:TStringList;
var i:integer;
begin
   Result:=TStringList.Create;
   Result.Add('Adam');
   Result.Add('Eva');
   Result.Add('Kain');
   Result.Add('Abel');
end;


procedure ProvideStringList(SL:TStringList);
var i:integer;
    Names:TStringList;
begin
   Names:=TStringList.Create;
   Names.Add('Adam');
   Names.Add('Eva');
   Names.Add('Kain');
   Names.Add('Abel');
   SL.Assign(Names);
   Names.Free;
end;


procedure TForm1.btn1Click(Sender: TObject);
var SL:TStringList;
    i:integer;
begin
   SL:=TStringList.Create;
   SL.Assign(GetStringList);
   for i:=0 to 3 do ShowMessage(SL[i]);
   SL.Free;
end;


procedure TForm1.btn2Click(Sender: TObject);
var SL:TStringList;
    i:integer;
begin
   SL:=TStringList.Create;
   ProvideStringList(SL);
   for i:=0 to 3 do ShowMessage(SL[i]);
   SL.Free;
end;

And now the question: what will happen to result object in function GetStringList:Tstringlist, which is created, but never freed? (I call 2 times Create and only 1 time Free) Is it memory safe to provide objects by function or should I use procedures to do this task, where object creation and destroying is simply handled (procedure ProvideStringlist)? I call 2 times Create and 2 times Free. Or is there another solution?

Thanx in advance

Lyborko

manpreet 2 years ago

var
   s : TStringList; 
begin
   s := GetStringList;
   // stuff
   s.free;
end;