Allgemein

There is a quite frequent question about how to correctly handle NULL values in Delphi using System.Json.TJSONObject.

Handling existing values, in this example, the array of „customers“ is fairly easy:

{"customers":[{"name":"Olaf"},{"name":"Big Bird"}]}

But what, if the array is „null“?

{"customers":null}

UPDATE 2019-12-16: Official patch available.

Unfortunately, the long-awaited Delphi 10.3.3 release also brought a few new issues. One of them is that TActionManager is broken in a way, that prevents projects, using it, from compiling.

Because of some scope issue, the IDE keeps adding a unit named „IDETheme.ActnCtrls.pas“ to any form unit, that contains a TActionManager, once you save that form unit. „IDETheme.ActnCtrls“ is invalid, does not exist, thus the whole project will not compile anymore.

Fortunately, until EMBT releases a hotfix, there is a relatively easy workaround:

• Add „VCL.ActnCtrls“ to any affected form unit
• Create and add a completely empty unit to your project and name that unit „IDETheme.ActnCtrls.pas“
• Compile

Single Sign-on with Facebook’s Login API and Delphi – my session at Coderage XII. Please see below for the link to the materials.

Download Sourcecode …

Supplying a username and a password has been standard for many years to grant access to protected applications. This works reasonably well, yet there are issues that you may want to address with your applications:

• shared passwords between apps, because it is easier to remember only a few passwords, than one password per application
• too easy to guess, non-strong passwords
• keeping your users passwords in a safe location
• missing protection for sensitive account actionsFacebook offers an API, that allows any application (desktop and mobile) to authenticate against Facebook account information, which basically implements single sign-on on a broad scope. A Facebook user only needs to create and keep track of his Facebook credentials. This password can be selected in a complex way as it is the only one that users need to remember, which makes it harder to guess. Facebooks also provides infrastructure and staff that actively protects their user database against any sorts of cyber attacks.

  In this session I demonstrate how to implement Facebook’s Login APIs in your Delphi application.

When you add lines to a TMemo in Delphi Applications, then you might want to scroll to the very end of that particular Memo, so that the newest lines are kept in view.

In FireMonkey it’s as easy as just calling GoToTextEnd:

procedure TFormMain.AddLog(AMessage: string);
begin
  Memo1.Lines.Add(AMessage);
  Memo1.GoToTextEnd;
end;

You might notice though, that when you clear the Memo at certain times, the scrollbars may get out of sync. To avoid that, you need to call ProcessMessages right after „clear“. Apparently the scrollbars get confused, when you add lines directly after clear command, because the actual position needs to be rendered first (which the ProcessMessages does).

procedure TFormMain.AddLog(AMessage: string);
begin
  if Memo1.Lines.Count > 100 then 
    begin
      Memo1.Lines.Clear;
      Application.ProcessMessages; //without this, scrollbars will show wrong size/position
    end;
  Memo1.Lines.Add(AMessage);
  Memo1.GoToTextEnd;
end;