Invalid Pointer Operation on TObjectList.DisposeOf - oop

Question

Hello folks and sorry if this is a duplicate but my specific issue I haven't seen answered anywhere yet.
I have an "Invalid Pointer Operation" when I try to free an ObjectList created at runtime at the following lines:
Prods := TItemProcedimento.Create(DM.FDQ).lerProdutos;
Prods.DisposeOf; // <- Invalid Pointer Operation at 2nd iteration
So, here's my classes:
unit uItemProcedimento;
interface
[...]
type
TItemProcedimento = class
[...]
public
constructor Create(DataSet: TFDQuery);
function lerProdutos: TObjectList<TItemProcedimento>;
[...]
constructor TItemProcedimento.Create(DataSet: TFDQuery);
begin
FDataSet := DataSet;
end;
function TItemProcedimento.lerProdutos: TObjectList<TItemProcedimento>;
begin
Result := TObjectList<TItemProcedimento>.Create;
try
FDataSet.Close;
FDataSet.SQL.Clear;
FDataSet.SQL.Add('SELECT *');
FDataSet.SQL.Add('FROM Produto p');
FDataSet.SQL.Add('JOIN ItensProcedimento IP on p.PRO_ID = IP.PRO_ID');
FDataSet.SQL.Add('ORDER BY p.PRO_Nome');
FDataSet.Open;
while not FDataSet.Eof do
begin
PRO_ID := FDataSet.FieldByName('PRO_ID').AsInteger;
PRO_Rendimento := FDataSet.FieldByName('PRO_Rendimento').AsInteger;
PRO_Nome := FDataSet.FieldByName('PRO_Nome').AsString;
PRO_Tipo := FDataSet.FieldByName('PRO_Tipo').AsInteger;
PRO_Custo := FDataSet.FieldByName('PRO_Custo').AsFloat;
PRO_Potencia := FDataSet.FieldByName('PRO_Potencia').AsFloat;
IPR_Uso := FDataSet.FieldByName('IPR_Uso').AsFloat;
Result.Add(self);
FDataSet.Next;
end;
finally
FDataSet.Close;
end;
The weirdest thing about this is that I have another class with the exact same behaviour and the method works without issues. Yes I am creating the object and immediately destroying it to test if I'm destroying it correctly.
In another class I have another example with the same code, but this time it works without errors
test := TMyClass.Create(DM.FDQ).lerTeste;
test.DisposeOf;
Why? What am I doing wrong? This test code is running before the current code btw, maybe its related?
UPDATE:
By applying the changes that Remy Lebeau suggested I managed to add properly the items to the list and dispose them so this particular part of the code has no leaks. But in another part of the code I have an ObjectList leak that I have no idea on how to fix.
Inside my class I have a property that is a TObjectList property, I have a method that checks if the list is assigned, if not, it creates it and returns it to whoever is calling the list.
[...]
type
TProcedimento = class
private
[...]
FPRC_Produtos: TObjectList<TItemProcedimento>;
public
[...]
function getPRC_Produtos: TObjectList<TItemProcedimento>;
function criaProcedimentos: TObjectList<TProcedimento>;
[...]
function TProcedimento.GetPRC_Produtos: TObjectList<TItemProcedimento>;
begin
if not Assigned(FPRC_Produtos) then
FPRC_Produtos:= TObjectList<TItemProcedimento>.Create;
result := FPRC_Produtos;
end;
function TProcedimento.criaProcedimentos: TObjectList<TProcedimento>;
var
IPR: TItemProcedimento;
Procedimento: TProcedimento;
ds: TFDQuery;
begin
result := TObjectList<TProcedimento>.Create;
ds := TFDQuery.Create(nil);
ds.Connection := FDataSet.Connection;
IPR := TItemProcedimento.Create(ds);
try
FDataSet.Close;
FDataSet.Open('SELECT * FROM Procedimento');
while not FDataSet.Eof do
begin
Procedimento := TProcedimento.Create(FDataSet);
Procedimento.PRC_ID := FDataSet.FieldByName('PRC_ID').AsInteger;
Procedimento.PRC_Nome := FDataSet.FieldByName('PRC_Nome').AsString;
Procedimento.PRC_Duracao := FDataSet.FieldByName('PRC_Duracao')
.AsDateTime;
Procedimento.PRC_Preco := FDataSet.FieldByName('PRC_Preco').AsCurrency;
Procedimento.PRC_Custo := FDataSet.FieldByName('PRC_Custo').AsCurrency;
Procedimento.PRC_Consumo := FDataSet.FieldByName('PRC_Consumo').AsFloat;
Procedimento.FPRC_Produtos := IPR.getItensProcedimento(FPRC_ID);
result.Add(Procedimento);
FDataSet.Next;
end;
finally
FDataSet.Close;
IPR.DisposeOf;
ds.DisposeOf;
end;
end;
I then use this property in a for-in loop to feed a list with the procs in my database
procedure TKBForm1.CarregaProcedimento;
var
Procedimento: TProcedimento;
Procs: TObjectList<TProcedimento>;
[...]
begin
Procs := TProcedimento.Create(DM.FDQ).criaProcedimentos;
try
LV_Procedimento.Items.Clear;
LV_Procedimento.BeginUpdate;
for Procedimento in Procs do
begin
with LV_Procedimento.Items.Add do
[...]
finally
Procs.DisposeOf;
Procedimento.GetPRC_Produtos.DisposeOf;
end;
end;
But there's still leaks happening after this part runs:
73 - 88 bytes: TProcedimento x 1, TItemProcedimento x 2
How do I fix this?