[Solved] DBGrid - how to catch exception with date editing?
lazarus / 16-Databases

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count · 2012-03-25 23:21

Hi All!
I've got a strange (imho) problem: can't find the way to catch
exception when tdatetime field is filled with "crap". Example project
in attach - very very basic - first colomn is of integer (and there is
no way to input "crap" there) nd the second - is of datetime. Try to
enter "some crap" there - and exception will be raised. How to catch
it? I dont want user to shut my programm pressing cancel button...
May be some compilation swithes?

Thanks in advance! any help apriciated!
(if forum mismatched - please fix)

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bambamns · 2012-03-26 03:53

Hi,

First , dealing with date can be sometimes tricky, because you will
find than lot of computers have different date format (different
county), and second, in my experience, it is no so wise to let user
edit data direct in database thru dbgrid - it is much better if you
make some fields out from dbgrid where user can put some data , and
you can control them and check before you make post/commit.
Using separate fields, in this case datetime picker, you will force
user to choose correct date format, and also you can check it (min or
max date) before you post/commit into database.

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count · 2012-03-26 10:53

Quote from: bambamns on March 26, 2012, 05:53:57 am ...in my
experience, it is no so wise to let user edit data direct in database
thru dbgrid - it is much better if you make some fields out from
dbgrid where user can put some data , and you can control them and
check before you make post/commit...

actually it's not a question of visual design - it's much more simple:
how to catch exception with poor data in dbgrid?

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JD · 2012-03-26 12:52

Quote from: count on March 26, 2012, 12:53:17 pmQuote from: bambamns
on March 26, 2012, 05:53:57 am ...in my experience, it is no so wise
to let user edit data direct in database thru dbgrid - it is much
better if you make some fields out from dbgrid where user can put some
data , and you can control them and check before you make
post/commit...

actually it's not a question of visual design - it's much more simple:
how to catch exception with poor data in dbgrid?

You're probably better off using the ZVDBDateTimePicker from the
ZVDateTimeControls package which has built in data validation
http://wiki.lazarus.freepascal.org/ZVDateTimeControls_Package. I've
found that it makes it very, very difficult for the user to input
"bad" dates. However, I myself believe it is not wise to let the user
enter data directly into the database using a DBGrid. Like bambamns
said, use normal form controls, validate the data and then post/commit
it to the database.

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ludob · 2012-03-26 13:03

When you use persistent fields you can create you own OnSetText event
handler for the "difficult" fields. There have full control of the
conversion and how data is stored in the database. If you fancy you
can even define your own custom dates such as 'today', etc.

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ludob · 2012-03-26 13:14

Another solution is to override the default exception handler:

Code: [Select]   TForm1 = class(TForm)
   private
     Procedure MyException(Sender : TObject; E : Exception);
...
procedure TForm1.MyException(Sender: TObject; E: Exception);
begin
  ShowMessage(E.Message);
end;
....
procedure TForm1.FormCreate(Sender: TObject);
begin
Application.OnException:=@MyException;
...
This will show the message and an OK button

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howardpc · 2012-03-26 14:42

Another solution if you want to input data directly via a DBGrid is to
create a DBGrid descendant that overrides the exception-catching code
for all cells linked to date fields. Something like:
Code: [Select]type
  { TDateExceptGrid }

  TDateExceptGrid=class(TDBGrid)
  protected
    procedure UpdateData; override;
  end;

  { TForm1 }

  TForm1 = class(TForm)
    Datasource1: TDatasource;
    MemDataset1: TMemDataset;
    procedure FormCreate(Sender: TObject);
  private
    FDateGrid: TDateExceptGrid;
  public
    { public declarations }
  end;

var
  Form1: TForm1;

implementation

{ TForm1 }

procedure TForm1.FormCreate(Sender: TObject);
begin
 FDateGrid := TDateExceptGrid.Create(Self);
 FDateGrid.Align := alClient;
 FDateGrid.DataSource:= Datasource1;
 FDateGrid.Parent:= Self;
end;

{$R *.lfm}

{ TDateExceptGrid }

procedure TDateExceptGrid.UpdateData;
var d: TDateTime;
begin
 if (SelectedField.DataType = ftDate) or (SelectedField.DataType =
ftDateTime) then
  if not TryStrToDate(Editor.Caption, d) then
   ShowMessageFmt('%s is an invalid date',[Editor.Caption])
 else
  inherited UpdateData;
end;

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count · 2012-03-26 16:19

Thank you howardpc, ludob!
It seems strange but in case of global exceptioon catch (on form)
everything is ok, but with tdbgreed descendant - exception is fired
twice. Any way - overriding default exception handler works fine.
Thanks again!