TField OnValidate: Bug or lack of understanding?
lazarus / 16-Databases

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kpeters58 · 2014-02-14 04:24

Goal: I want to selectively respond to certain exceptions.

To this end, I trap my application's exceptions via a
TApplicationProperties.OnException event.

To illustrate the issue, assume that I have a TDBEdit hooked up to a
float field. All CRUD operations work just fine. Now I want to
introduce field validation, so for this field's OnValidation event I
have

Code: [Select]  if Sender.AsCurrency < 10.0 then
    DatabaseError('Value must be 10.0 or bigger'); 
When run in the debugger, I see the expected EDatabaseError with my
message on an attempt to save a value of less than 10.0 - so far, so
expected. But after that, a second? exception pops up saying that
whatever value I entered is an invalid float, which is a message I do
NOT want to show my users.

I have tried using a custom exception as well (which I initially see)
and which then, too, is followed by a second exception of type
EDatabaseError with the same message as stated above - and now I
cannot even filter by my custom exception type as the exception being
trapped is the 2nd one.

Just in case someone is tempted to say: Why don't you validate in
OnExitEvents or such - I am well aware of these and do not want to use
them.

Bug or feature?

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LacaK · 2014-02-15 20:57

Can you reproduce it with simple database application scenario, where
are not used DB-aware controls like TDBEdit ?

So only any TDataSet with Field with OnValidate event handler and you
use:

FieldByName('MyField').AsFloat:=1; //here should be raised error in
OnValidate

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kpeters58 · 2014-02-16 05:41

Good catch: Works as expected if no DB-aware components are being
used.

What made you think of your suggestion?

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LacaK · 2014-02-17 06:36

Quote from: kpeters58 on February 16, 2014, 06:41:41 amGood catch:
Works as expected if no DB-aware components are being used.

What made you think of your suggestion?
Only intuition