On May 8, 2009, at 1:30 PM, Chuck Hill wrote:
Hi Charles,
Welcome!
On May 7, 2009, at 5:20 PM, Charles Young wrote:
Hi
I'm sure I have a commonly seen issue:
I have a many to many relationship between tables SOURCE and DEST.
This is implemented by a third table GLUE which contains the PKs of
SOURCE and DEST as well as an integer property (order) that
describes the order of DESTs with respect to SOURCE.
This might not be so common. A more common thing is to order them
by an attribute of DEST.
I'd like to flatten the relationship such that I can call a method
like:
source.dests() -> NSArray <Dest>
where the array is ordered by source.glue.order().
I've written a simple method that grabs source.glue(), sorts it on
glue.order() and then iterates to extract dest, but I'm sure this
issue has been solved many, many times before in a cleaner and more
elegant manner.
I can't think of another way. You could encapsulate this in a
generic method using Key-Value coding so that you only had to write
it once.
If you are using Wonder, here's what I will usually do in this
situation:
public NSArray<Dest> sortedDests() {
NSArray<Glue> sortedGlues = glues(null,Glue.ORDER.ascs());
return (NSArray<Dest>) sortedGlues.valueForKey(Glue.DEST);
}
Which, as Chuck suggests, can then be abstracted from the specific
entities using KVC so you don't have to rewrite it for each many-to-
many relationship. But it's not a lot of code anyway.
On a separate subject thanks to all for a very interesting and
informative group. I've been lurking for some time and have been
enjoying the various conversations.
:-)
Especially the goat herding threads, I bet. :-)
Are you coming to WOWODC?
Dave
Chuck
--
Chuck Hill Senior Consultant / VP Development
Come to WOWODC'09 in San Fran this June!
http://www.wocommunity.org/wowodc09/
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