Question

I have a core data entity called images that has just 2 fields:

imageName = NSString
timeStamp = NSNumber

I am trying to simulate a kind of stack LIFO (last in first out).
Inserting a new entry is easy but what about reading the last entry added to the entity?

All images are added with a timestamp, obtained by using

time_t unixTime = (time_t) [[NSDate date] timeIntervalSince1970];

an integer that is equal to the number of seconds since 1970

so, how do I retrieve the last inserted record of a core data (= the record that has the biggest timestamp number)???

thanks

Answer 1

Perform a fetch request, sorting the results by timeStamp.

NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:...];

// Results should be in descending order of timeStamp.
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"timeStamp" ascending:NO];
[request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];

NSArray *results = [managedObjectContext executeFetchRequest:request error:NULL];
Entity *latestEntity = [results objectAtIndex:0];

You might also want to restrict the number of results using NSFetchRequest‘s setFetchLimit:.