Newbie question about Memory Leak with TJSONObject

[lfgarrido]

Hello guys

I have this Login Procedure in LoginForm:

procedure TfrmLogin.btnLoginClick(Sender: TObject);
var
  Return : TJSONObject;
begin
  Return := TJSONObject.Create;
  try
    try
      UniMainModule.RESTClient1.BaseURL := 'http://someurl.com/api';
      UniMainModule.RESTRequest1.Resource := 'login';
      UniMainModule.RESTRequest1.Method := rmPOST;
      UniMainModule.RESTRequest1.Params.ParameterByName('j_username').Value := edtUser.Text;
      UniMainModule.RESTRequest1.Params.ParameterByName('j_password').Value := edtPassword.Text;
      UniMainModule.RESTResponse1.ContentType := 'application/json';
      UniMainModule.RESTRequest1.Execute;

      Return := UniMainModule.RESTResponse1.JSONValue as TJSONObject;
    except
      on E: Exception do 
	  ShowMessage(E.Message);
    end;
  finally
    Return.Free;
  end;
end;

 

But when I shutdown the StandAlone Server I got a Memory Leak:

---------------------------
Unexpected Memory Leak
---------------------------
An unexpected memory leak has occurred. The unexpected small block leaks are:
1 - 12 bytes: TDictionary<Data.Bind.Components.TBasicBindComponent,Data.Bind.ObjectScope.TBindSourceAdapterLink>.TValueCollection x 3, TRESTResponseAdapter.TNotify x 1, TRESTRequestAdapter.TNotify x 1, TRESTComponentNotifyList<REST.Client.TCustomRESTRequest.TNotify> x 1, TCookieManager x 1, TRESTClientAdapter.TNotify x 1, TBindEventList1<System.Integer> x 3, TBindEventList x 9, TRESTComponentNotifyList<REST.Client.TCustomRESTClient.TNotify> x 1, TCredentialsStorage x 1, Unknown x 3
13 - 20 bytes: TValueReaderFunc<System.JSON.TJSONValue> x 1, TValueReaderFunc<System.Classes.TStrings> x 1, TValueReaderFunc<System.Integer> x 2, TCustomRESTRequest.TBody x 1, TBindSourceAdapterLink x 3, TList x 2, TJSONObject x 1, TValueWriterProc<System.string> x 6, TValueReaderFunc<System.string> x 14, UnicodeString x 1, Unknown x 9
21 - 28 bytes: @TRESTComponentAdapter.CreateReadOnlyField$ActRec<System.JSON.TJSONValue> x 1, @TRESTComponentAdapter.CreateReadOnlyField$ActRec<System.Classes.TStrings> x 1, @TRESTComponentAdapter.CreateReadOnlyField$ActRec<System.Integer> x 2, @TRESTComponentAdapter.CreateReadOnlyField$ActRec<System.string> x 8, TRESTRequestAdapter.AddParameterFields.MakeParameterField$ActRec x 2, TRESTClientAdapter.AddPropertyFields$ActRec x 1, UnicodeString x 41, Unknown x 19
29 - 36 bytes: TRESTRequestAdapter.CreatePropertyFields$ActRec x 1, TRESTRequestParameter x 2, @TRESTComponentAdapter.CreateReadWriteField$ActRec<System.string> x 6, TRESTHTTP x 1, TRESTRequestParameterList x 5, TScopeMappings x 6, TNativeImageRecord x 9, UnicodeString x 32
37 - 44 bytes: TRESTComponentAdapter.TReadField<System.JSON.TJSONValue> x 1, TRESTComponentAdapter.TReadField<System.Classes.TStrings> x 1, TRESTComponentAdapter.TReadField<System.Integer> x 2, TList<REST.Client.TCustomRESTRequest.TNotify> x 1, TIPHTTPRequest x 1, TList<System.Net.URLClient.TCertificate> x 1, TList<System.Net.HttpClient.Win.PCERT_CONTEXT> x 1, TCookies x 2, TList<System.Net.URLClient.TCredentialsStorage.TCredential> x 1, TList<Data.Bind.ObjectScope.TBaseObjectBindSource> x 3, TList<System.Classes.TNotifyEvent> x 12, TList<System.Classes.TCollectionItem> x 11, TList<Data.Bind.Components.TBasicBindComponent> x 6, TList<REST.Client.TCustomRESTClient.TNotify> x 1, TList<System.Classes.TComponent> x 14, TUniJSHelper x 1, TRESTComponentAdapter.TReadField<System.string> x 8, TList<System.JSON.TJSONPair> x 1, UnicodeString x 26
45 - 52 bytes: TUniMask x 1, TObjectList<Data.Bind.ObjectScope.TBindSourceAdapterLink> x 3, TObjectList<Data.Bind.ObjectScope.TBindSourceAdapterField> x 3, TRESTComponentAdapter.TReadWriteField<System.string> x 6, UnicodeString x 7, Unknown x 1
53 - 60 bytes: TObjectDictionary<System.string,System.Net.URLClient.TURLClient> x 1, TIPProxyConnectionInfo x 1, TObjectDictionary<Data.Bind.Components.TBasicBindComponent,Data.Bind.ObjectScope.TBindSourceAdapterLink> x 3
61 - 68 bytes: UnicodeString x 5, Unknown x 2
69 - 76 bytes: TStringList x 4, TRESTResponseAdapter.AddPropertyFields$ActRec x 1, UnicodeString x 3
77 - 84 bytes: UnicodeString x 3
85 - 92 bytes: UnicodeString x 1, Unknown x 2
101 - 108 bytes: TWinHTTPResponse x 1
109 - 116 bytes: UnicodeString x 2
117 - 124 bytes: UnicodeString x 4, Unknown x 1
133 - 140 bytes: Unknown x 2
157 - 172 bytes: TWinHTTPRequest x 1, TWinHTTPClient x 1
173 - 188 bytes: TUniNativeImageList x 1
189 - 204 bytes: TSubRESTResponseBindSource x 1, TSubRESTRequestBindSource x 1, TSubRESTClientBindSource x 1, TRESTClient x 1
205 - 220 bytes: UnicodeString x 1, Unknown x 1
221 - 236 bytes: TRESTResponse x 1
253 - 268 bytes: TRESTRequest x 1
269 - 284 bytes: Unknown x 1
301 - 316 bytes: TUniMainModule x 1
349 - 380 bytes: TRESTResponseAdapter x 1, TRESTRequestAdapter x 1, TRESTClientAdapter x 1
The sizes of unexpected leaked medium and large blocks are: 4396, 8748

 

If I just comment this line bellow keeping Return Object empty I don't get a Memory Leak message

// Return := UniMainModule.RESTResponse1.JSONValue as TJSONObject;

 

I know that is not a question directly about uniGUI, but I realy appreciate some tips and best pratices.

Tks

[Jean-Marc Kiener]

The RESTResponse creates and returns a valid TJSONObject. You do not have to create one first, i think. Comment out and see what's happened..

//Return := TJSONObject.Create;

Edited January 13, 2020 by Jean-Marc Kiener
text edit

[lfgarrido]

Thanks for the answer @Jean-Marc Kiener but I still got a memory leak even commenting the unnecessary create of Return object.

But used https://jsontodelphi.com/ to create a class for representing my JSON, and I did with successfull without memory leaks.

I will keep my study to undertand what happened with my previous approach to avoid this in the future.

Tks again!