TObject als Übergabeparameter

[sniper_w]

Ich stelle hier eine DoubleLinked-List die (bei mir ) funktioniert...:

Delphi-Quellcode:

type
 TListNode = class(TObject)
   private
     FNext:TListNode;
     FPrev:TListNode;
   public
     procedure AfterConstruction();override;
     procedure BeforeDestruction();override;
   published
     property Next:TListNode read FNext;
     property Prev:TListNode read FPrev;
 end;

 TDoubleLinkedList = class(TObject)
   private
     FHead:TListNode;
     FTail:TListNode;
     FSize:Integer;
   protected
   public
     procedure AfterConstruction();override;
     procedure BeforeDestruction();override;
     procedure Append( Node:TObject );
     procedure InsertBefore( Node, Before:TObject );
     procedure Remove( var Node:TObject; AndDelete:Boolean = False );
     function NextNode( Node:TObject ):TObject;
     function PrevNode( Node:TObject ):TObject;
     procedure Clear();
   published
     property Size:integer read FSize;
     property Head:TListNode read FHead;
     property Tail:TListNode read FTail;
 end;

implementation

uses
  SysUtils;

{ TListNode }

procedure TListNode.AfterConstruction();
begin
  inherited;
  FNext := nil;
  FPrev := nil;
end;

procedure TListNode.BeforeDestruction();
begin
  inherited;
end;

{ TDoubleLinkedList }

procedure TDoubleLinkedList.AfterConstruction();
begin
  inherited;
  FHead := nil;
  FTail := nil;
  FSize := 0;
end;

procedure TDoubleLinkedList.Clear();
  var Node:TListNode;
begin
  while FHead <> nil do
  begin
    Node := FHead;
    FHead := FHead.FNext;
    Node.Free;
  end;
end;

procedure TDoubleLinkedList.BeforeDestruction();
begin
  Clear();
end;

procedure TDoubleLinkedList.Append( Node:TObject );
begin
  if FHead = nil then
  begin
    FHead := TListNode(Node);
    FTail := TListNode(Node);
  end else
  begin
    TListNode(Node).FPrev := FTail;
    FTail.FNext := TListNode(Node);
    FTail := TListNode(Node);
  end;
  Inc(FSize);
end;

procedure TDoubleLinkedList.InsertBefore( Node, Before:TObject );
begin
  if FHead = nil then
  begin
    FHead := TListNode(Node);
    FTail := TListNode(Node);
  end else
  begin
    if Before = FHead then
    begin
      TListNode(Node).FNext := FHead;
      FHead.FPrev := TListNode(Node);
      FHead := TListNode(Node);
    end else
    begin
      TListNode(Node).FNext := TListNode(Before);
      TListNode(Node).FPrev := TListNode(Before).FPrev;
      TListNode(Node).FPrev.FNext := TListNode(Node);
      TListNode(Before).FPrev := TListNode(Node);
    end;
  end;
  Inc(FSize);
end;

procedure TDoubleLinkedList.Remove( var Node:TObject; AndDelete:Boolean );
begin
  if Node = nil then
  begin
    Exit;
  end;

  if Node = FHead then
  begin
    FHead := FHead.FNext;
    if FHead = nil then
      FTail := nil
    else
      FHead.FPrev := nil;
  end 
  else if Node = FTail then
  begin
    FTail := FTail.FPrev;
    if FTail = nil then
      FHead := nil
    else
      FTail.FNext := nil;
  end else
  begin
    TListNode(Node).FPrev.FNext := TListNode(Node).FNext;
    TListNode(Node).FNext.FPrev := TListNode(Node).FPrev;
  end;
  Dec(FSize);
  TListNode(Node).FNext := nil;
  TListNode(Node).FPrev := nil;
//  if AndDelete then
//  begin
//    TListNode(Node).Free();
//    Node := nil;
//  end;
end;

function TDoubleLinkedList.NextNode( Node:TObject ):TObject;
begin
 if Node = nil then
   Result := nil
 else
   Result := TListNode(Node).FNext;
end;

function TDoubleLinkedList.PrevNode( Node:TObject ):TObject;
begin
 if Node = nil then
   Result := nil
 else
   Result := TListNode(Node).FPrev;
end;