Ordering IN()

August 9th, 2019

This post is not about DoorDash or SkipTheDishes, it’s about using the Where IN() clause in SQL. Yesterday I thought I had discovered a way to order the inclusion of child records since this StackOverflow answer led me to believe that ordering values in the IN() clause will in fact order the resultset in Firebird. Unfortunately, in my testing with Firebird 3.04 this is not the case.

So beware, StackOverflow can be a great source of information, but it’s not always correct. It’s also of course better to explicitly order results rather than rely on the behaviour of a query processing engine so I will be re-writing the Marshmellow code used to generate the query.

Linux Compiler will remain an Enterprise Only Feature

August 9th, 2019

In case you have not been watching RSP-17195 Marco just closed the ticket yesterday. Apparently EMBT has decided that the Linux compiler will remain an Enterprise edition feature and will not appear in the Pro edition as requested.

I have written before as to why I think this a major marketing mistake, so just briefly, Linux is used by more hobbyist programmers and IoT/SBC developers than most other OSes, and there are many FOSS solutions available. Few people interested in targeting Linux will pay for the Enterprise Edition as they can target a Windows machine and pay the M$ license cheaper than buying an Enterprise edition. It also makes no sense to allow the targeting of Windows and MacOS in the Pro edition, but not the other desktop target. I think this is the same mistake that was made when originally selling the Mobile AddOn, which EMBT later decided to include in Pro in order to limit development costs and increase the user base. Licensing FMXLinux will likely not amount to much of an incentive as my understanding is most developers who have currently licensed the Enterprise edition are writing server apps. Increasing the cost of writing a desktop app will not encourage the uptake of hobbyist or professional developers looking to monetize apps on a platform that users typically prefer FOSS solutions.

Other vendors like REMObjects do not charge additional money for a product edition to target a supported platform. You get all platforms for the same subscription price, and they have now written an RTL and WASM support which makes their platform that much more attractive to Delphi developers. REMObjects also has 64 bit ARM target support today.

.NET cannot be ignored now that .NET Native and Core have been released and are rapidly maturing. Delphi’s “native” compilation is no longer an advantage and the C# code generated tends to be more efficient than Delphi’s various compilers by all accounts.

You can have the greatest product in the world, but if you cannot sell it to a sufficiently large user base, it will not be self sustaining. Marketing decisions like this IMHO will negatively impact the Delphi user base.

Delphi Now Has Linux UI Support

June 26th, 2019

Just announced, FMXLinux has been licensed from KSDev for inclusion in the Enterprise and Architect editions of RAD Studio and related products (Delphi & C++ Builder).  The product is available via GetIt for all current subscribers.

Since I have been following FMXLinux’s development for some time, I immediately installed the licensed version.  Unfortunately, the IDE experience is the same as the trial I previously installed directly from KSDev.

I created a new Multi-device application with tabbed navigation from the wizard.  Looking at the list of target platforms (Android, Mac OS, iOS, Windows) I didn’t see Linux.  Fair enough, the templates on which the application is based do not contain the new UI platform.  Perhaps in a subsequent release since as per Marco’s introduction the product has not been fully integrated into the IDE.

I went to add the new platform to the solution, by Rt. clicking The Target Platforms node in the project manager and it is greyed out.  If I delete a target it is re-enabled, but the list of targets I can add only contains the one I just deleted.  Rt. Clicking on the Application node in Projects window, there is an option “Add Linux Platform”.  Now I get a Linux 64 bit target platform node.

This is covered in Marco’s introduction, but he doesn’t mention that attempting to add a component to my UI doesn’t work.  I can’t add a button to my form until I switch to another target platform, and then switch back so I can actually deploy and test on Linux.  This has been a known issue with the trial, and I was hopeful that such a poor user experience would be fixed now that EMBT has licensed the product.  For now, it’s an issue you will have to work around, and I’m sure it will be corrected in a future release.

While only major Linux distros are currently supported (Ubuntu, RedHat and possibly a couple others) the team at KSDEV are working to support others including the more obscure ones like Elementary OS.  I for one am very pleased that Delphi finally can target Linux with GUI applications making it a complete XPlatform desktop solution for all 3 major targets.

Android - The case of the vanishing file

June 22nd, 2019

I’m relatively new to the Android development platform, coming from the Windows desktop. One of the great things about recent editions of Delphi is it’s ability target numerous other platforms. One of the worst things about recent versions of Delphi is it’s ability to target platforms you are not as familiar with. If your use case is atypical, you can quickly find yourself swimming in shark infested waters. You never know what is going to byte you, a bug in the platform, a bug in Delphi RTL or FMX code, a bug in your code, or just your lack of knowledge about the platform.

Today I was trying to figure out why files I was saving to the Documents folder on my Android LG5 were visible from the Android File Manager, but not present when I connected the phone to a Windows, or Ubuntu desktop. Turns out there is a long outstanding bug in Android that google has not even acknowledged. In order to see new files when connecting to a device using the MTP protocol, you may need to re-boot the Android device before the files appear. Indeed once I did so, my files appeared and I could copy them off to my PC. You may want to comment on this motion to get the issue re-opened and addressed.

Hopefully this helps someone else avoid spending a lot of time scratching their head…

JIRA is Down

May 16th, 2019

Just a note to EMBT customers, JIRA has been down for several hours now.  It is currently giving the following message

HTTP Status 500 - org.ofbiz.core.util.GeneralRuntimeException: Could not determine database type. (Network error IOException: Connection refused: connect)

With a Java callstack if you like that kind of thing.  EMBT has been advised and I’ve been told EDN may also be affected. Hopefully it will be back up shortly.

More Persistence with Spring4D ORM

May 15th, 2019

Today I decided to ensure the project I am working on is in fact database independent. The best way I have found is to make sure you develop and test on multiple databases as you go. Since the ORM portion of Spring4D often called Marshmellow is supposed to isolate your application from the underlying data store, I figured it would be a piece of cake.

The Spring4D ORM supplies numerous database adapters including UIB (Unified Interbase). There is also another I found for IBX. I decided to try UIB since I want minimal deployment dependencies and am using Firebird, but was a little concerned since the last commit was from Jun 13, 2016.

After pulling down the source code from the repo I discovered that there are no projects for Delphi Rio, so I copied the projects for the last version (21) and renamed them to create Rio projects. Getting the components installed proved quite easy, but once I had the basic data ORM setup code for an alternate database incorporated into my project, that’s when the fun started.

Initially UIB would not load the GDS32.DLL from c:\Windows\System32 that was generated from my Firebird 3.0 Win64 install. Providing the full path did not resolve the issue, and GetLastError() wasn’t helpful so I changed the client library to fbclient, and the app crashed a little further down the line.

The ORM uses a TDatabaseManager class to build the database structures from the registered entity metadata when you call the BuildDatabase method.  It worked for SQLLite, but did not for Firebird as the database file did not exist. Unfortunately the TDatabaseManager was never designed to be extended. The class contains only private fields with no protected accessors, and the constructor as well as the BuildDatabase method, are not virtual. As a result I wrote the following decorator class to provide the extended functionality:

type
  TUIBDatabaseManager = class(TObject)
  private
    FConnection :IDBConnection;
    FUIBConnectionAdapter :TUIBConnectionAdapter;
    FDatabaseManager :TDatabaseManager;
    procedure CreateTheDatabase;
  public
    constructor Create(const connection: IDBConnection);
    procedure BuildDatabase;
  end;

implementation

uses
  Spring.Persistence.SQL.Interfaces, {for TQueryLanguage}
  uiblib;

procedure TUIBDatabaseManager.BuildDatabase;
begin
  //if the database does not exist then create it
  if not FileExists(FUIBConnectionAdapter.Connection.DatabaseName) then
    CreateTheDatabase;

  FDatabaseManager.BuildDatabase;
end;

constructor TUIBDatabaseManager.Create(const connection: IDBConnection);
begin
  FConnection := connection;
  FConnection.QueryLanguage := qlFirebird;
  FDatabaseManager := TDatabaseManager.Create(FConnection);
  FUIBConnectionAdapter := connection as TUIBConnectionAdapter;
end;

procedure TUIBDatabaseManager.CreateTheDatabase;
begin
  FUIBConnectionAdapter.Connection.CreateDatabase(TCharacterSet.csWIN1252);
end;

After I got the database created, the application bombed because it was attempting to create boolean object fields as BIT database columns. Tracing through the code I found the where the datatype mapping was performed and added a snippet for FireBird 3 support after descovering that UIB already supported the Boolean datatype for Interbase and Firebird. All I had to do was compile UIB with the FB30 directive. Here is the amended version of the GetSQLDataTypeName method:

function TFirebirdSQLGenerator.GetSQLDataTypeName(
  const field: TSQLCreateField): string;
begin
  Result := inherited GetSQLDataTypeName(field);
  {add support for Firebird 3.0/Interbase 7 new boolean datatype}
  {$ifdef FB30}
  if (field.TypeInfo.Kind = tkEnumeration) and
     (field.typeInfo = System.TypeInfo(Boolean)) then
    Result := 'BOOLEAN'
  else
  {$endif}
  if StartsText('NCHAR', Result) then
    Result := Copy(Result, 2, Length(Result)) + ' CHARACTER SET UNICODE_FSS'
  else if StartsText('NVARCHAR', Result) then
    Result := Copy(Result, 2, Length(Result)) + ' CHARACTER SET UNICODE_FSS';
end;

Once I got that issue resolved the app crashed on a SQL snippet I had in a call to the ExecuteSQL method because Firebird likes quoted identifiers when you use mixed case column names. Once I had worked around that I found that Firebird threw many more errors importing data due to my Column attributes than SQLLite had. It also complained because I had used a reserved word in Firebird as a table name. After a some more fixups I had a running application capable of using either database back end. In the process I re-discovered how much I like Firebird, even if some of it’s SQL error messages are rather cryptic. It is also much faster importing data that SQLLite.

Persistence with Spring4D

May 14th, 2019

My blog tagline is certainly no accident.  I have been interested in persistence frameworks for a long time, and thought I would use Spring4D’s Marshmellow ORM for a project.  Spring4D has been around for quite some time and just had it’s first conference in Italy so I figured the framework was mature and warranted a closer look.  I had previously used the Spring4D DI container, and decided this time to use Spring4D collections as well to avoid as much code bloat as possible.

The first thing I discovered is that the Spring persistence layer aka Marshmellow has a very unfortunate name.  Trying to google it with “delphi” leads to all sorts of hits related that Android version.  The next thing I learned is that development has been put on hold as of September 2018 due to a lack of resources.  This is unfortunate, as there are not that many open source ORMs that use the newer language features of Delphi when compared C# or Java.

The third thing I quickly learned is that other than the Tests, there is not a whole lot of documentation available.  There is the reference help which is really not that helpful.  It doesn’t contain descriptions of the class interactions or architecture and has no examples of usage.  Really it’s not much more informative than drilling through the code.  The best source of “getting started” help that I could find is the previous bitbucket repo. There is of course also the google groups if you need to get clarification of something, and reading previous posts can help you from running into common issues.

As a newbie, it’s not clear how the [InheritenceAttribute()] works so I will have to investigate it further. I assume if the last descendant in a class hierarchy is the only one marked as an entity, it will by default have all the fields marked with the Column() attribute in all ancestor classes.

Another thing that is not particularly clear from any documentation is how the underlying datatype employed by the database is determined.  There are really only 3 pertinent parameters supplied to the Column() attribute, namely length, precision and scale.  Length only applies to string types and precision, scale to numeric.  It is unclear how precision and scale effectively change the numeric datatype and it’s corresponding precision or scale, other than for Integer datatypes you specify 0,0 for precision,scale.

I’m sure all this will become clear as I use the framework more, but some more thorough ‘Getting Started’ documentation would have been really nice.

How to get Login Dialogs Appearing on the TaskBar

May 9th, 2019

Most of the applications I have worked on in Delphi are database apps that may present a splash form quickly followed by a login dialog.  If the user fails to authenticate, the application needs to terminate gracefully.  The only way to do so cleanly is to modify the DPR code with some conditional logic. I’ve seen scenarios where after the main form was created the login dialog was invoked and if authentication failed everything was torn down. This complicates the shutdown logic, and often didn’t work well, encouraging a call to Halt() and sometimes leaving the process in memory.

Any long time Delphi user knows that messing with the generated DPR code in Delphi can cause all sorts of grief later when Delphi tries to auto create forms and add units to the uses clause.  That is out of scope for this post, suffice to say that it is possible to write something like this:

var
  User :TUser;
begin
  Screen.Cursor := crAppStart;
  try
    Application.Initialize;
    Application.MainFormOnTaskbar := True;
    Application.Title := 'My Secure App';
    Application.CreateForm(TMainDm, MainDm);
  finally
    Screen.Cursor := crDefault;
  end;
  User := TfrmLogin.Login
  (
    function (const UserName,Password :string) :TObject
    begin
      Result := MainDm.Session.FindWhere<TUser>(
        Restrictions.&And(
          Restrictions.Eq('UserName',UserName),
          Restrictions.Eq('Password',Password)
        )
      ).FirstOrDefault;
    end,
    {
      UserName can be passed as first parameter so don't
      have to type it in all the time
    }
    ParamStr(1),
    3  {credential retries available }
  ) as TUser;
  if User <> nil then
  begin
    Application.CreateForm(TfrmMain, frmMain);
    frmMain.CurrentUser := User;
    Application.Run;
  end;
end.

The problem is that the Login Dialog does not appear on the Windows Taskbar. If it is hidden behind other windows, the user may think the application has not been launched and attempt to start another instance. There is no easy way for the user to bring the login dialog to the foreground short of closing other windows that may be in front of it. Putting the form on the taskbar solves this. As a quick solution I looked at the SetMainForm method in the Vcl.Forms unit, and decided to extract the ChangeAppWindow() procedure since it is not available outside of the Forms unit. Then I simply called it from this event, and voila! a taskbar button showing the Login form.

procedure TfrmLogin.FormCreate(Sender: TObject);
begin
  ChangeAppWindow(handle,True,True);
end;

I’m sure there are reasons why this method is not exposed as a public TApplication class procedure, but perhaps it could be with a usage caveat.

EF Core - Burning the Database to the Ground

February 1st, 2019

During development, you sometimes want to make database changes that a migration cannot handle.  One such example is changing the datatype of a primary key column from an int to bigint.  In such a case you may want to burn the database to the ground and have a single migration that creates all the database structures defined through the model to date.  Some developers routinely remove all migrations to “cleanup” the code.

The procedure to do so is different for EF vs EF Core, and if you don’t do it the right way, things can get screwed up and be hard to fix.  With EF Core the easiest way I have found to burn the database to the ground is to use the PMC command:

update-database 0

This is a little different than simply removing all the database tables from a SQL utility like SMS.  It actually removes all tables, but ensures that the __EFMigrationsHistory table is present with 0 rows.

Then you can create delete all the files in the Migrations folder of the C# project and create a new initial migration:

add-migration "Some Title"

and generate the new structures:

update-database

Elementary - Sherlock’s OS?

December 20th, 2018

Recently the hard drive in my Toshiba Satellite gave up the ghost, so I decided to stick in an SSD and update the OS.  Originally the laptop shipped with Windows 8 (yeach!).  The laptop kept hanging as it accessed the hard drive.  I tried repairing it by booting off a Windows CD, but it kept locking up.  Even after installing a new SSD this issue persisted.  I could not get any version of Windows to install.

Finally I decided that I would try to install a Linux Distro.  I had previously used Ubuntu and found it to be reasonably reliable and user friendly,  Googling for Distro rankings I came across Elementary OS.  It’s Mac like UI intrigued me, so I set about installing it.  Unlike Windows, the Linux distro installed without issue on my SSD, and seems quite quick.

I happily discovered that Firefox and Skype are available and work quite well although installing them was a little more complicated than running a Windows installer.  Unfortunately I cannot say the same for VMWare Player, so for now running my VMs on the laptop is not possible.  Between the apps that come bundled, and those available for this Ubuntu based Linux distro, I have everything an average use would need on a daily basis.

Unfortunately I installed Loki (v4) and to “upgrade” to the latest OS version of Juno (v5.0) meant a complete re-install of the OS and apps.  Hopefully future “upgrades” will be available using the AppCentre.