• Subject: Re: Externalize DB/IO (was What Counts as Technically Slick?)
  • From: Douglas Handy <dhandy1@xxxxxxxxxxxxx>
  • Date: Mon, 09 Apr 2001 19:49:11 -0400

Nathan,

>You might notice it's missing a lot of I/O
>related error checking, data validation, etc.  

(snip)

>But that's the sort of logic the UI control module
>doesn't need to worry about.  Also consider how dbAdd() handles all data
>validation without the UI control module worrying about it.  

To play Devil's Advocate here, let's take the example of dbAdd data validation
and the user interface.  Let's say dbAdd fails and returns a message in dbMsg,
which then propagates to wsuMsg for display.

How does the UI portion highlight the field(s) related to the error message, and
position the cursor for the user?  With multiple errors, I expect all of the
fields to get highlighted, an error message subfile to have all the message
texts (although admittedly few users roll it), and the first field in error to
have the cursor positioned to it.

And I further expect the message subfile to be in the order the fields appear on
the screen.  Or at least the very first message better be for the field where
the cursor got positioned (and that needs to be the top highlighted field).

How does dbAdd know which error happens to be the top field in error on this
particular display format so dbMsg has a reasonable text (assuming it is a
single text string)?

A trigger program or constraint can easily enforce business rules.  But how do
you then communicate that back to the UI layer in the manner they have used for
the last 20 years?

IMHO, it is simply not acceptable to put the cursor back at the top of the
screen with a generic message, or even a specific message which relates to
something near the bottom of the screen when other errors exist higher on the
screen.

So what do you do?

Doug
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