Getting started with libraries
rcozens at pon.net
Sun Mar 19 11:52:22 EST 2006
> So for me the issue is how to reach this point from where I am today.
> Has anyone any advice about shifting my existing code into libraries
> without having to massively restructure my existing apps?
First, you have my sincere condolences.
Second, you've made a wonderful case for the need for library stacks
Third, it will be a pain in the arse; but the longer you wait, the
worse things will get and the greater the task will become.
> So far all I have thought of is to remove the 'common' code to a
> library but to retain the handler that was in the original app simply
> as a wrapper - a wrapper handler would look like
> on myOldHandler para1, para2
> do myLibraryStuff para1,para2
> end myoldHandler
A little good news: unless your scripts contain declared local
variables, there's a good chance this step is not necessary.
Given a control with a script including
put field "Quantity" into para1
put field "Unit Cost" into para2
put the result into field "Total Cost"
on myOldHandler para1,para2
set the numberFormat to "#.00"
add (it*taxRate) to it
repeat for each line shippingRate in shippingTable
if item 1 of shippingRate >= it then
add item 2 of shippingRate to it
-- assumes last line of shipping table covers largest
, all you have to do is copy myOldHandler to the library stack, remove
it from the control's script, and start using the library stack when
the stack containing the control opens.
> However I have been (I suppose) rather careless with ways of passing
> values, using various techniques including setting globals, specific
> fields etc. If the library is not to have too many side effects then I
> have to generalise those routines too, and that's the bit which I
> would like to do as efficiently as possible. Maybe it's just a messy
> job and that's all there is about it, but I'd like to know what other
> people think.
I hate to confirm what you don't want to hear; but, yes, it ends up
being a messy job for the reasons you identified: creating a
generalized handler from two or more similar handlers in different
stacks often means changing the scripts in both. To the extent that
your common handlers are generic, you might adopt your controls to use
handlers in existing rev libraries rather than generalizing your
handlers as well as the scripts of controls that call them. Serendipity
Library <http://wecode.org/serendipity/> includes handlers for data
validation & formatting, date & time handlers, and list handlers in
addition to SDB database handlers.
The good news: when you are finished, the efficiency you will gain is
worth much more than the effort involved.
CCW, Serendipity Software Company
"And I, which was two fooles, do so grow three;
Who are a little wise, the best fooles bee."
from "The Triple Foole" by John Donne (1572-1631)
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