I usually cache it in the EO itself but I also add a refreshCaches()
method that I call when
something modifies the object graph in such a way that the cached
relationships may be
out of date. The refreshCaches method simply nulls out the private
NSArray. The accessor
then checks for null and only fetches if necessary.
Alan
On Aug 11, 2009, at 9:32 AM, Michael Halliday wrote:
Hi List,
Let's say you have in your model:
Customer -->> Transactions
Since a customer could have 1000's or 10000's transactions ...
obviously you wouldn't want to have transactions as a class property
on the Customer EO for performance reasons. Normally you would
never want to get at ALL the transactions for a customer at once,
but you might want to get "Open" transactions or "Flagged"
transactions. So, for example you could have a method on the
Customer EO that just fetches the Transaction with a qualifier as
below:
public NSArray<Transaction> openTransactions() {
return Transaction.fetchTransactions(editingContext(),
Transaction.CUSTOMER.eq(this).and(Transaction.STATUS.eq("Open")),
null);
}
Now, this is all well and good ... but what's the "best practice"
for caching this result? You wouldn't want to bind this method up
to a WORepetition for example! I'd just be curious to see how other
people are handling these situations. Do you cache this stuff in
the EO itself ... or do you just limit calls to such methods and
cache the return value? I'm basically describing the role of Core
Data's fetched properties.
Cheers,
Michael
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