筆記使用Array Sort來排序自己做的物件

  NSSortDescriptor *sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"object_name" ascending:YES] autorelease];
  NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
  NSArray *sortedArray  = [MyWantSortArray sortedArrayUsingDescriptors:sortDescriptors];