對NSArray中的ManagedObjects做排序

NSArray *recordMOArray = [self.petInfoMO.recordEntities allObjects];

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:NO];

    NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];

    NSArray *sortedArray = [recordMOArray sortedArrayUsingDescriptors:sortDescriptors];

    

    NSDate* end = [NSDate date];

    NSDate* start = ((RecordMO *)[sortedArray firstObject]).date;