TZConnection.DesignConnection and embedded FB

[FrankBKK]

Today I run into a rather curious issue with zConnection.DesignConnection when using Firebird3 Embedded.

When zConnection.DesignConnection = True and zConnection.Database property points to a FDB that does not exist on runtime the application just quits - no error message or anything. Naturally one thinks of a wrongly configured Embedded Server, issues with the connection strings etc. but for sure the last thing that comes to mind is a DesignTime property ...

That was even more annoying as Zeos seems to check on that before the DataModule's OnCreate event is triggered, so no chance for a proper debug session

What exactly is DesignConnection supposed to do and what other effects can I expect during runtime ?

[marsupilami]

Hello Frank,

When zConnection.DesignConnection = True and zConnection.Database property points to a FDB that does not exist on runtime the application just quits - no error message or anything. Naturally one thinks of a wrongly configured Embedded Server, issues with the connection strings etc. but for sure the last thing that comes to mind is a DesignTime property ...

That was even more annoying as Zeos seems to check on that before the DataModule's OnCreate event is triggered, so no chance for a proper debug session

Erm - this is natural to Delphi. Design time properties get applied during the creation of DataModules and Forms. Zeos has to act as soon as properties get set.

What exactly is DesignConnection supposed to do and what other effects can I expect during runtime ?

This is what DesignConnection does at runtime:

Code: Select all

{**
  This method is required to support proper component initialization.
  Without it, the connection can start connecting before every property is loaded!
}
procedure TZAbstractConnection.Loaded;
begin
  inherited Loaded;
  try
    if FStreamedConnected then
      if (csDesigning in ComponentState) or not FDesignConnection then
        SetConnected(True);
  except
    if csDesigning in ComponentState then
      if Assigned(Classes.ApplicationHandleException) then
        Classes.ApplicationHandleException(ExceptObject)
      else
        ShowException(ExceptObject, ExceptAddr)
    else
      raise;
  end;
end;

FStreamedConnected gets set to True, during the deserialization of the connection component if you set Connected = True at designtime. So basically DesignConnection is a property that says "I might have set Connected to true at designtime but I don't want to automatically connect at runtime. I want that connection at designtime only."

So - usually setting DesignConnection to true should be a safe way to handle things.

Best regards,

Jan

[FrankBKK]

Hi Jan,

thanks for your prompt and extensive reply.

So - usually setting DesignConnection to true should be a safe way to handle things.

Hmm, the way you explain it I would agree - that is until the FDB set at design time does not exist at runtime (which I would say is the norm).

I just can't wrap my head around the fact that a design time property - set correctly or wrong - causes the runtime application to simply quit without further notification - I would at least expect an error to be raised.

[marsupilami]

I just can't wrap my head around the fact that a design time property - set correctly or wrong - causes the runtime application to simply quit without further notification - I would at least expect an error to be raised.

Hmm - this is a part, that I don't understand too. Maybe you can prepare a small sample application that demonstrates the problem? Also I would have to know which Compiler and IDE you use, including version numbers.

Best regards,

Jan