字段存空值判断

• (NSDictionary *)deleteAllNullValue{
  NSMutableDictionary *mutableDic = [[NSMutableDictionary alloc] init];
  for (NSString *keyStr in self.allKeys) {
  if ([[self objectForKey:keyStr] isEqual:[NSNull null]]) {
  [mutableDic setObject:@"" forKey:keyStr];
  }
  else{
  [mutableDic setObject:[self objectForKey:keyStr] forKey:keyStr];
  }
  }
  return mutableDic;
  }