Encode NSString for XML/HTML

Question

Is there a way to HTML encode a string (NSString) in Objective-C, something along the lines of Server.HtmlEncode in .NET?

Answer 1

Here is a more efficient implementation of this xml escape logic.

+ (NSString*) xmlSimpleEscape:(NSString*)unescapedStr
{
  if (unescapedStr == nil || [unescapedStr length] == 0) {
    return unescapedStr;
  }

  const int len = [unescapedStr length];
  int longer = ((int) (len * 0.10));
  if (longer < 5) {
    longer = 5;
  }
  longer = len + longer;
  NSMutableString *mStr = [NSMutableString stringWithCapacity:longer];

  NSRange subrange;
  subrange.location = 0;
  subrange.length = 0;

  for (int i = 0; i < len; i++) {
    char c = [unescapedStr characterAtIndex:i];
    NSString *replaceWithStr = nil;

    if (c == '\"')
    {
      replaceWithStr = @""";
    }
    else if (c == '\'')
    {
      replaceWithStr = @"'";
    }
    else if (c == '<')
    {
      replaceWithStr = @"<";
    }
    else if (c == '>')
    {
      replaceWithStr = @">";
    }
    else if (c == '&')
    {
      replaceWithStr = @"&";
    }

    if (replaceWithStr == nil) {
      // The current character is not an XML escape character, increase subrange length

      subrange.length += 1;
    } else {
      // The current character will be replaced, but append any pending substring first

      if (subrange.length > 0) {
        NSString *substring = [unescapedStr substringWithRange:subrange];
        [mStr appendString:substring];
      }

      [mStr appendString:replaceWithStr];

      subrange.location = i + 1;
      subrange.length = 0;
    }
  }

  // Got to end of unescapedStr so append any pending substring, in the
  // case of no escape characters this will append the whole string.

  if (subrange.length > 0) {
    if (subrange.location == 0) {
      [mStr appendString:unescapedStr];      
    } else {
      NSString *substring = [unescapedStr substringWithRange:subrange];
      [mStr appendString:substring];
    }
  }

  return [NSString stringWithString:mStr];
}

+ (NSString*) formatSimpleNode:(NSString*)tagname value:(NSString*)value
{
  NSAssert(tagname != nil, @"tagname is nil");
  NSAssert([tagname length] > 0, @"tagname is the empty string");

  if (value == nil || [value length] == 0) {
    // Certain XML parsers don't like empty nodes like "", use "" instead
    return [NSString stringWithFormat:@"<%@ />", tagname];
  } else {
    NSString *escapedValue = [self xmlSimpleEscape:value];
    return [NSString stringWithFormat:@"<%@>%@", tagname, escapedValue, tagname];    
  }
}