Trying to calculate a running total using Core Data
Trying to calculate a running total using Core Data
- Subject: Trying to calculate a running total using Core Data
- From: Felix Rodriguez <email@hidden>
- Date: Mon, 21 Apr 2008 04:06:39 -0400
I am trying to figure out how to calculate a running total using core
data. I have created an entity called Transactions that have the
following properties.
Transactions
amount
balance
I am trying to calculate the balance by adding up the amount of all
the previous balances. I have subclased NSManagedObject and
overridden awakeFromFetch. Here is the code I have so far.
- (void)awakeFromFetch
{
[super awakeFromFetch];
double amount = [[self valueForKey:@"amount"] doubleValue];
[self setValue:[NSNumber numberWithFloat:amount]
forKey:@"balance"];
}
This routine only copies the amount to the balance property. I am
thinking that I have to Query all of the previous transactions and
calculate their totals. I know how to create a NSFetchRequest on a
transaction object but I am unsure on how to create the NSPredicate
object to extract all the transactions that were created prior to the
current transaction. Thanks for any help you can provide.
_______________________________________________
Cocoa-dev mailing list (email@hidden)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden