//字符串 转Unicode

• (NSString *)utf8ToUnicode:(NSString *)string{

  NSUInteger length = [string length];
  NSMutableString *str = [NSMutableString stringWithCapacity:0];
  for (int i = 0;i < length; i++){
  NSMutableString *s = [NSMutableString stringWithCapacity:0];
  unichar _char = [string characterAtIndex:i];
  // 判断是否为英文和数字
  if (_char <= '9' && _char >='0'){
  [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i,1)]];
  }else if(_char >='a' && _char <= 'z'){
  [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i,1)]];
  }else if(_char >='A' && _char <= 'Z')
  {
  [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i,1)]];
  }else{
  // 中文和字符
  [s appendFormat:@"\u%x",[string characterAtIndex:i]];
  // 不足位数补0 否则解码不成功
  if(s.length == 4) {
  [s insertString:@"00" atIndex:2];
  } else if (s.length == 5) {
  [s insertString:@"0" atIndex:2];
  }
  }
  [str appendFormat:@"%@", s];
  }
  return str;

}

//Unicode 转字符串

• (NSString *)replaceUnicode:(NSString *)unicodeStr
  {

  NSString *tempStr1 = [unicodeStr stringByReplacingOccurrencesOfString:@"\u"withString:@"\U"];
  NSString *tempStr2 = [tempStr1 stringByReplacingOccurrencesOfString:@"""withString:@"\""];
  NSString *tempStr3 = [[@"""stringByAppendingString:tempStr2] stringByAppendingString:@"""];
  NSData tempData = [tempStr3 dataUsingEncoding:NSUTF8StringEncoding];
  NSString returnStr = [NSPropertyListSerialization propertyListFromData:tempData
  mutabilityOption:NSPropertyListImmutable
  format:NULL
  errorDescription:NULL];
  return [returnStr stringByReplacingOccurrencesOfString:@"\r\n"withString:@"\n"];
  }