NSSortDescriptor *des = [NSSortDescriptor sortDescriptorWithKey:@"key" ascending:YES];
NSArray *sortedArr = [array sortedArrayUsingDescriptors:[NSArray arrayWithObject:des]];
NSSortDescriptor *des = [NSSortDescriptor sortDescriptorWithKey:@"key" ascending:YES];
NSArray *sortedArr = [array sortedArrayUsingDescriptors:[NSArray arrayWithObject:des]];