Delete from

BIZ TMS Aurelius
1

In this code...


procedure TfrmPrincipal.Button1Click(Sender: TObject);
var
  manager: TObjectManager;
  Grupos: TList<TGrupos>;
  Grupo: TGrupos;
begin
  manager := TObjectManager.Create(connSQLite);
  try
    Grupos := manager.Find<TGrupos>().List;
    for Grupo in Grupos do
      manager.remove(Grupo);
  finally
    manager.Free;
  end;
end;

the line ->  manager.remove(Grupo); returns for me Access Violation... 

Something i'm doing wrong?
2

How is TGroups class declared and implemented? What is the call stack at the point of Access Violation?

3
procedure TfrmPrincipal.Button1Click(Sender: TObject);
var
  manager: TObjectManager;
  Grupos: TList<TGrupos>;
  Grupo: TGrupos;
begin
  manager := TObjectManager.Create(connSQLite);
  try
    Grupos := manager.Find<TGrupos>().List;
    for Grupo in Grupos do
      showmessage(Grupo.Grupo);
    // manager.remove(Grupo);
  finally
    manager.Free;
  end;
end;

In this line -> manager.remove(Grupo); all commands work(save, saveorupdate, etc), except the remove...

In this code all groups are displayed correctly with showmessage.

Exception: First chance exception at $00AF044E. Exception class $C0000005 with message 'access violation at 0x00af044e: read of address 0x00000004'.

Environment: 
-Windows 7
-Delphi 10.1 Berlin and Delphi 10.2 Tokyo
4

How is TGroups class declared and implemented? What is the call stack at the point of Access Violation?


I can only guess that you have a recursive mapping (TGroups maps to TGroups) with a cascade set, so when you Remove a group, you also remove related groups. Thus it might be you are removing a TGroups that is already destroyed. With recursive mapping there isn't much you can do, you must manually take of that and be sure you are not accessing a group that has been already destroyed.
5

Hello, i found what was the problem. Analyzing the class i found the property TColumnProp.Lazy and so it became easier to understand the error. But, how should REMOVE be done in this case?


CLASS
[Column('IMAGEM', [TColumnProp.Lazy])]
FIMAGEM: TBlob;
6

I don't understand how TColumnProp.Lazy is related to the mentioned error? Can you please explain better?

You should have no issue in removing an object with lazy properties. 
7

ok, i'll send the code


Class
  [Entity, AutoMapping]
  [Id('FCD_GRUPO', TIdGenerator.None)]
  TGrupos = class
  private
    [Column('CD_GRUPO', [TColumnProp.Required])]
    FCD_GRUPO: Integer;

    [Column('GRUPO', [], 50)]
    FGRUPO: Nullable<string>;

    [Column('IMAGEM', [TColumnProp.Lazy])]
    FIMAGEM: TBlob;

    [Column('SUB_ASSOCIADO', [], 50)]
    FSUB_ASSOCIADO: Nullable<string>;

    [Column('GRUPO_DELIVERY', [])]
    FGRUPO_DELIVERY: Nullable<Integer>;
    // FGRUPO_DELIVERY: Nullable<Boolean>;

    [Column('GRUPO_MESA', [])]
    FGRUPO_MESA: Nullable<Integer>;
    // FGRUPO_MESA: Nullable<Boolean>;
  public
    property CD_GRUPO: Integer read FCD_GRUPO write FCD_GRUPO;
    property GRUPO: Nullable<string> read FGRUPO write FGRUPO;
    property IMAGEM: TBlob read FIMAGEM write FIMAGEM;
    property SUB_ASSOCIADO: Nullable<string> read FSUB_ASSOCIADO
      write FSUB_ASSOCIADO;
    property GRUPO_DELIVERY: Nullable<Integer> read FGRUPO_DELIVERY
      write FGRUPO_DELIVERY;
    property GRUPO_MESA: Nullable<Integer> read FGRUPO_MESA write FGRUPO_MESA;

IMPLEMENTATION

ON CREATE
TMappingExplorer.Default.GetTable(TComplemento).Name := 'GRUPOS'; 
//Only to learn how to set table with AUTOMAPPING

procedure TfrmPrincipal.btnRemoveClick(Sender: TObject);
var
  Manager: TObjectManager;
  Grupos: TList<TGrupos>;
  Grupo: TGrupos;
begin
  Manager := TObjectManager.Create(conn);
  try
    Grupos := Manager.Find<TGrupos>().List;
    for Grupo in Grupos do
    begin
      Manager.remove(Grupo); //EXCEPTION IN THIS LINE
    end;
  finally
    Manager.Free;
  end;
end;


PS: When we remove the blob field from the class or remove the TColumnProp.Lazy property from it, the error has not ocurred any more.

PS2: The Class was exported with DataModeler
8

I still don't see any problem. Are you able to create a small project that reproduces the problem with a SQLite database? If you can send to me I can debug and check what's wrong.

9
We were able to simulate the error with the Echo example, inserting only a new property in the TCustomer Class of type TBlob with TColumnProp.Lazy.

CLASS
type
  [Entity, Automapping]
  TCustomer = class
  private
    FId: TGuid;
    FName: string;
    [Column('IMAGEM', [TColumnProp.Lazy])]
    FImage:TBlob;
  public
    property Id: TGuid read FId write FId;
    property Name: string read FName write FName;
    property Image: TBlob read FImage write FImage;
  end;


When trying to delete by AureliusDataSet, we recived the same error.

ERRO: "First chance exception at $006AE95D. Exception class $C0000005 with message 'access violation at 0x006ae95d: read of address 0x00000004'. Process EchoBasicDemo.exe (10656)"

If you want, we can send the modified project to your email, so that you can analyze
10
Link of broken project

https://www.xpointsolucoes.com.br/basic.rar


11

Ok, you didn't mention you were using TMS Echo. We were able to reproduce and fix the problem, it's caused by the TMS Echo logger. If you need a patch before we release a new version with this fix, please send us an e-mail directly asking for the patch.