[Resolved] Feature Request need lnDeleting in TList.Notify
lazarus / 64-FPC development

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Zaher · 2022-10-22 17:39

I inherited TObjectList, and used TList.Notify to work with my own
hash list in the list, I need to recive deleted item before freed by
Object List that own that items.
lnDeleted is call after this item really deleted and freed, I think 
we need new one "lnDeleting" to call before deleting the item.

Code: [Select]procedure TList.Delete(Index: Integer);
var P : pointer;
begin
  P:=FList.Get(Index);
  if assigned(p) then
    Notify(p, lnDeleting);
  FList.Delete(Index);
  if assigned(p) then
    Notify(p, lnDeleted);
end;

Thank in advance.

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ASerge · 2022-10-23 10:55

Quote from: Zaher on October 22, 2022, 07:39:36 pmI inherited
TObjectList, and used TList.Notify to work with my own hash list in
the list, I need to recive deleted item before freed by Object List
that own that items.
lnDeleted is call after this item really deleted and freed, I think 
we need new one "lnDeleting" to call before deleting the item.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i type 
TMyObjList = class(TObjectList)  protected    procedure Notify(Ptr:
Pointer; Action: TListNotification); override;  end; procedure
TMyObjList.Notify(Ptr: Pointer; Action: TListNotification);begin  if
Action = lnDeleted then    WorkWithItemBeforeFree(Ptr)  else   
inherited;end;

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Zaher · 2022-10-24 12:06

Works now thank you so much.

I used this in another place, but I have complicated list inheritance
and I got crash on removing line, It seem FPC compiler mess with me,
It not recompile my changed unit (idk why)
I will mark as solved

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Thaddy · 2022-10-24 13:30

The proper way is to use observer/observed:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i {$MODE
OBJFPC}{$APPTYPE CONSOLE} uses Classes; type  TMyObject =
class(TObject)  strict private    FName: string;  public   
constructor Create(const AName: string);    destructor Destroy;
override;  end;   TFreeObjectObserver = class(TInterfacedObject,
IFPObserver)    procedure FPOObservedChanged(ASender: TObject;
Operation: TFPObservedOperation; Data: Pointer);  end; constructor
TMyObject.Create(const AName: string);begin  inherited Create;  FName
:= AName;end; destructor TMyObject.Destroy;begin  Writeln(#9'Item ''',
FName, ''' destroy');  inherited;end; procedure
TFreeObjectObserver.FPOObservedChanged(ASender: TObject; Operation:
TFPObservedOperation; Data: Pointer);begin  if Operation =
ooDeleteItem then    TObject(Data).Free;end; procedure Test;var  L:
TList;  Observer: TFreeObjectObserver;begin  Observer :=
TFreeObjectObserver.Create;  try    L := TList.Create;    try     
L.FPOAttachObserver(Observer);      Writeln('Populate list');     
L.Add(TMyObject.Create('Zero'));      L.Add(TMyObject.Create('One')); 
    L.Add(TMyObject.Create('Two'));     
L.Add(TMyObject.Create('Three'));      Writeln('Set item 0 to nil'); 
   L[0] := nil;      Writeln('Delete item 2');      L.Delete(2);     
Writeln('End of using list');    finally      L.Free;    end; 
finally    Observer.Free;  end;end; begin  Test;  Readln;end.This is
all standard code and supported by the RTL. Only dependency is
classes.