[Solved] Where is EDatabaseError defined
lazarus / 16-Databases

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dokhebi · 2012-12-11 21:09

Using Laz 1.0.4 & FPC 2.6.0 on WinXP.

I want to catch an exception like this:

Code: [Select]  try
    MySQL51Connection1.Connected := True;
  except
    On E: EDatabaseError do
      begin
        ShowMessage('Could not connect to database');
        Close;
      end;
  end;

but I get the following message:

Code: [Select]main.pas(53,11) Error: Identifier not found
"EDatabaseError"
main.pas(53,26) Error: class type expected, but got "<erroneous type>"
main.pas(69) Fatal: There were 2 errors compiling module, stopping

Where is EDatabaseError defined?  Is there a package/unit I need to
include to make it work?

Thanks in advance.

Edward Hooper

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BlueIcaro · 2012-12-11 21:39

It's on unit DB.
More info: http://www.freepascal.org/docs-
html/fcl/db/edatabaseerror.html

/BlueIcaro

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dokhebi · 2012-12-11 22:00

I included unit DB so it compiles, but it's not catching the
exception.  Is there a property in the application or the control that
states I will handle all exceptions?

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Zoran · 2012-12-11 22:39

Quote from: dokhebi on December 11, 2012, 11:00:03 pmI included unit
DB so it compiles, but it's not catching the exception.  Is there a
property in the application or the control that states I will handle
all exceptions?

Perhaps the raised exception is not EDatabaseError?

Try something like this:
Code: [Select]  try
    MySQL51Connection1.Connected := True;
  except
    on E: Exception do begin
      if E is EDatabaseError then
        ShowMessage('Could not connect to database')
      else
        ShowMessage('Raised Exception: ' + E.ClassName + LineEnding +
'with message:' + E.Message);
    end;
  end;

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BigChimp · 2012-12-12 06:57

You can also catch multiple exceptions like this (air code, typed in
this post, not tested) - go from most specific exception to least
specific:
Code: [Select]  try
    MySQL51Connection1.Connected := True;
  except
// you can also do on C: E... database specific error (e.g. defined in
ibconnection, mssqlconnection etc depending on which db you use. These
often give some more detailed error messages)
    on D: EDatabaseError do begin
        ShowMessage('Database error is raised.')
    end;
    on E: Exception do begin
        ShowMessage('Raised Exception: ' + E.ClassName + LineEnding +
'with message:' + E.Message);
    end;
  end;

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dokhebi · 2012-12-12 19:04

I found out what was happening.  The Lazarus environment runs the
debugger by default so it catches the exception first.  I would click
on Break in the pop-up message and the program would pause.  When I
click on Continue it lets the exception handler code do its thing. 
When I run the compiled binary outside of Lazarus it behaves as
expected.

Thanks for the help.

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BlueIcaro · 2012-12-12 20:47

Quote from: dokhebi on December 12, 2012, 08:04:23 pmI found out what
was happening.  The Lazarus environment runs the debugger by default
so it catches the exception first.  I would click on Break in the pop-
up message and the program would pause.  When I click on Continue it
lets the exception handler code do its thing.  When I run the compiled
binary outside of Lazarus it behaves as expected.

Thanks for the help.
That  is the correct way that debuger works in Lazarus, and as i
remenber in the version of  Delphi that I used.

/BlueIcaro