classes (objects) instead of records

 

I need to use a class instead of record for VirtualStringTree node.

Should I declare it standard (but in this case - tricky) way like that: 

PNode = ^TNode;
TNode = record
 obj: TMyObject;
end;
//..
var
 fNd: PNode;
begin
fNd:= vstTree.getNodeData(vstTree.AddChild(nil));
fNd.obj:= TMyObject.Create; 
//..

or should I use directly TMyObject ? If so - how?! How about assigning (constructing) the object and freeing it?

Thanks in advance m.

  • Setup datasize for holding object 

    vstTree.NodeDataSize := SizeOf(TMyObject);

  • Get the datasize holder and bind to your object 

    vstTree.getNodeData(passed in interested node)^ := your object

    or 

    vstTree.getNodeData(vstTree.AddChild(nil))^ := TMyObject.Create;

    or
    use vstTree.InsertNode method

  • To free the binding object hookup the OnFreeNode event 

    vstTree.OnFreeNode := FreeNodeMethod;

    with 

    procedure TFoo.FreeNodeMethod(Sender: TBaseVirtualTree; Node: PVirtualNode);
var
  P: ^TMyObject;
begin
  P := Sender.getNodeData(Node);
  if P <> nil then
  begin
      P^.Free;
      P^ := nil; //for your safety or you can omit this line
  end;
end;

    • you could create the object instance after receiving the node data, as in : 

    fNd:= vstTree.getNodeData(vstTree.AddChild(nil)); 
fnd.obj := TMbyObject.Create;

    or you could try and assign it directly

    Pointer(Obj) := vstTree.getNodeData(...);

    你可以在OnFreeNode事件中释放你的对象。

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