Update Core Data records <fault> - ios

Question

I m trying to update some records in Core Data. I m adopting following steps to get it done
Fetch function with predicate retrieves the records from the Core Data
Store the result set in a Object Array
Loops through the array and update each record
Call save context
I m running into two problems
After Initial run i get < fault > in the log
I m not sure whether the save context will actually save the object
My code:
- (void)fetchExpenses {
// Define our table/entity to use
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Expense" inManagedObjectContext:managedObjectContext];
// Setup the fetch request
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entity];
// Define how we will sort the records
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"timestamp" ascending:NO];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"publishTimestamp == nil"];
[request setPredicate:predicate];
// Fetch the records and handle an error
NSError *error;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if (!mutableFetchResults) {
// Handle the error.
// This is a serious error and should advise the user to restart the application
}
// Save our fetched data to an array
[self setExpenseArray: mutableFetchResults];
[mutableFetchResults release];
[request release];
}
- (void) save: {
[self fetchExpenses];
int i = 1;
int max = [expenseArray count];
for(i=1; i<=max; i++) {
// Get the expense selected.
Expense *expense = [expenseArray objectAtIndex: i];
// Do your updates here
[expense setTimestamp:2]
}
}

Answer 1

The fault you are seeing in the log doesn't indicate an error but means that the managed object is not fully loaded into memory but is instead represented by a fault object. This is normal behavior. When you try to access or change an object attribute the full object will be "faulted" or read-in to memory. It's a confusing old-fashion database terminology that dates back to 1960s.
Your code does not save any objects. Changes to managed objects in memory will not be persisted until you call a save on the managed object context.
You also do not want to use a mutable copy like this:
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
… because it waste memory and can lead to duplicate managed objects. There was some code in Apple docs that got this started but its erroneous. Instead, just use:
NSArray *fetchResults=[managedObjectContext executeFetchRequest:request error:&error];
… which will return an autoreleased array of the managed objects matching the fetch.