Hi all,
I'm just thinking through a couple of problems and wondered if anyone
had anything to say about it...
In my app I have several things that apply on a "per document" level,
for example, the mapping from Quartz co-ordinate values to some other
measurement system, such as millimetres. Different documents might
have different mappings. Other parts of my interface will want to work
with these settings, for example text fields that set geometric
properties such as line width. Many of these text fields live in
floating palettes that respond to different document windows becoming
main, etc.
So what I'm thinking is that I can write a custom formatter attached
to the text fields that can pick up the current main document's co-
ordinate mappings. I'm just not sure what the most efficient and most
straightforward implementation might look like.
I could get every formatter instance to subscribe to certain
notifications, but that requires a lot of code to set up and tear down
as nibs are loaded, etc. Alternatively, I could give the formatter
some class methods that centralise the notification handling and also
keep track of all the individual instances. Trouble with that is that
class methods are global, rather than "per document", though since
most (but not all) of the formatters are also global in the sense that
they are in context sensitive palettes, that is favourite at the moment.
Or maybe formatters are not a sensible way to deal with this at all?
Is there a better design pattern I'm overlooking?
--Graham
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