Enforcing constraints
lazarus / 16-Databases

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kpeters58 · 2015-04-21 16:55

The fact that TField's CustomConstraint and ConstraintErrorMessage are
not yet implemented, makes dealing with missing values that much more
cumbersome.

The default message that is generated, while technically correct, is
designed to scare the crap out of people running the program with its
additional warning: 'Press OK to ignore and risk data corruption.
Press Cancel to kill the program.".

My question is: How do you guys handle NOT NULL constraints in your
programs?

I am currently using the CaptureExceptions property and the
OnException handler from TApplicationProperties to centrally handle
these, but am wondering if there are better ways...

PS: Using the SqlDB framework

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taazz · 2015-04-21 17:17

have you seen the events of the query? especially the onupdateerror,
onediterror, and onPostError?

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kpeters58 · 2015-04-21 17:57

Probably the first method I tried out - I am a big believer in simple,
clear & techo-speak free error messages for the users of my programs.

Thus I'd have to parse the component names out because they should not
be visible as they provide no value at all to end users - they are
confusing at best.

The moment I do that, I make my programs vulnerable to framework
changes because my parsing might fail should someone alter the format
of the database exceptions - I'd much rather have working
CustomConstraints or something else....