core date排序

//排序条件
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc]initWithKey:@"updateDate" ascending:YES];  //根据updateDate来排序，ascending：YES＝＝》升序

　　　//添加多个排序条件！
        NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
        [fetchRequest setSortDescriptors:sortDescriptors];
       
        [sortDescriptor release];
        [sortDescriptors release];