[Solved] TThreadList Free objects?

[lainz]

Hi, I'm manipulating a list of objects in multiple threads, one for adding and other for iteration / removing items.

I found TThreadList, and seems ok, but I have a doubt about freeing the objects, this way is ok?

I've implemented only in the destructor, but I need as well in the Remove item method, if is ok in the destructor I will do the same there.

Thanks.

Code: Pascal  [Select][+][-]

1.    TEstadoMercadoPagoItem = (empPendiente, empAprobado, empVisto);
2.  
3.    { TMercadoPagoItem }
4.  
5.    TMercadoPagoItem = class(TObject)
6.    public
7.      iMesa: Integer;
8.      rTotal: Real;
9.      sReferencia: String;
10.      sEstado: TEstadoMercadoPagoItem;
11.      constructor Create(AMesa: Integer; ATotal: Real; AReferencia: String);
12.    end;
13.  
14.    { TMercadoPagoList }
15.  
16. TMercadoPagoList = class(TThreadList)
17.      destructor Destroy; override;
18.    end;
19.  
20. var
21.   MercadoPagoList: TMercadoPagoList;
22.  
23.   implementation
24.  
25.   { TMercadoPagoList }
26.  
27.     destructor TMercadoPagoList.Destroy;
28.     var
29.       i: integer;
30.       list: TList;
31.       p: TPointer;
32. begin
33.   list := LockList;
34.   try
35.     for i:=list.Count-1 downto 0 do
36.     begin
37.       p := list.Items[i];
38.       list.Remove(p);
39.       TMercadoPagoItem(p).Free;
40.     end;
41.   finally
42.     UnlockList;
43.   end;
44.   inherited Destroy;
45. end;

[lainz]

Or if that is not as good, is possible to use records with TThreadList? Since my object just holds data, there are no internal methods involved.. Thanks.

[lucamar]

TThreadList uses an internal TList which is returned by LockList so you can add an observer to it and free whatever needs to be freed in the notification handler.

However, if you're sure you'll never use that feature you can (and probably should) either override the default Remove method or sub-class TThreadList to add a new RemoveAndFree() method to take care of that.

HTH!

ETA: And yes, you can use almost anything: records, classes, simple types, ... As TList, TThreadList deals only with pointers so you can use whatever you can get a pointer from.

[lainz]

Thanks, so I will use records.

[lainz]

I had to use objects because records didn't work.
I have to edit the content once added...

[lucamar]

There should be no problem, only with records you have to remember to dereference the pointer, because it's not automagically done like with (new-style) objects, so something like:

Code: Pascal  [Select][+][-]

1.   p := list.Items[i];
2.   p^.sEstado := emAprobado;
3.   { Or just ... }
4.   list.Items[i]^.rTotal := 300.50;

Of course, nothing inherently "wrong" in doing it with objects/classes; only it's somewhat "wasteful" if a simple (or even an advanced) record would suffice.

[lainz]

There should be no problem, only with records you have to remember to dereference the pointer, because it's not automagically done like with (new-style) objects, so something like:

Code: Pascal  [Select][+][-]

1.   p := list.Items[i];
2.   p^.sEstado := emAprobado;
3.   { Or just ... }
4.   list.Items[i]^.rTotal := 300.50;

Of course, nothing inherently "wrong" in doing it with objects/classes; only it's somewhat "wasteful" if a simple (or even an advanced) record would suffice.

Thanks, yes maybe that was the problem, I never did programming with pointers and records.

[lucamar]

Thanks, yes maybe that was the problem, I never did programming with pointers and records.

It's not very difficult but it requires a little more attention to details such as when you're dealing with the pointer and when with the thing it points to, where is that thing: local/stack or heap, whether you need to reserve memory or is reserved by a declaration, etc.

Funny things like those