HTML entity encoding (convert '<' to '<') on iPhone in objective-c - iphone

Question

I'm developing an application for the iPhone that has inApp-mail sending capabilities. So far so good, but now I want to avoid html-injections as some parts of the mail are user-generated texts.
Basically I search for something like this:
// inits
NSString *sourceString = [NSString stringWithString:#"Hello world! Grüße dich Welt <-- This is in German."];
// ----- THAT'S WHAT I'M LOOKING FOR
// pseudo-code |
// V
NSString *htmlEncodedString = [sourceString htmlEncode];
// log
NSLog(#"source string: %#", sourceString);
NSLog(#"encoded string: %#", htmlEncodedString);
Expected output
source string: Hello world! Grüße dich Welt <-- This is in German.
encoded string: Hello world! Grüße dich Welt <-- This is in German.
I already googled and looked through several of SO's questions and answers, but all of them seem to be related to URL-encoding and that's not what I really need (I tried stringByAddingPercentEscapesUsingEncoding with no luck - it creates %C3%BC out of an 'ü' that should be an ü).
A code sample would be really great (correcting mine?)...
--
Thanks in advance,
Markus

Answer 1

Check out my NSString category for HTML. Here are the methods available:
- (NSString *)stringByConvertingHTMLToPlainText;
- (NSString *)stringByDecodingHTMLEntities;
- (NSString *)stringByEncodingHTMLEntities;
- (NSString *)stringWithNewLinesAsBRs;
- (NSString *)stringByRemovingNewLinesAndWhitespace;

Answer 2

Thanks #all. I ended up using my own implementation:
//
// _________________________________________
//
// textToHtml
// _________________________________________
//
- (NSString*)textToHtml:(NSString*)htmlString {
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"&" withString:#"&"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"<" withString:#"<"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#">" withString:#">"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"""" withString:#"""];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"'" withString:#"'"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"\n" withString:#"<br>"];
return htmlString;
}

Answer 3

A little improvement on #Markus' code [Change <br /> to <p></p>, escape multiple spaces]
- (NSString*)textToHtml:(NSString*)htmlString {
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"&" withString:#"&"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"<" withString:#"<"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#">" withString:#">"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"""" withString:#"""];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"'" withString:#"'"];
htmlString = [#"<p>" stringByAppendingString:htmlString];
htmlString = [htmlString stringByAppendingString:#"</p>"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"\n" withString:#"</p><p>"];
// htmlString = [htmlString stringByReplacingOccurrencesOfString:#"\n" withString:#"<br />"];
while ([htmlString rangeOfString:#" "].length > 0) {
htmlString = [htmlString stringByReplacingOccurrencesOfString:#" " withString:#" "];
}
return htmlString;
}

Answer 4

I have been looking for a similar solution and this did the job for me
NSString* value = #"<&>";
const void* keys[1] = {CFSTR("somekey")};
const void* values[1] = {value};
CFDictionaryRef dicRef = CFDictionaryCreate(kCFAllocatorDefault, keys, values, 1, nil, nil);
CFDataRef dataRef = CFPropertyListCreateData(kCFAllocatorDefault, dicRef, kCFPropertyListXMLFormat_v1_0, 0, NULL);
NSString *str = [[NSString alloc]initWithData:(NSData *)dataRef encoding:NSUTF8StringEncoding];
NSRange start =[str rangeOfString:#"string>"];
NSRange end =[str rangeOfString:#"</string"];
NSString *substr = [str substringWithRange:NSMakeRange(start.location+start.length, end.location-(start.location+start.length))];
[str release];
CFRelease(dicRef);
CFRelease(dataRef);
//Substring is now html entity encoded
I am using some of the features that is used when saving plist files. I hope this helps.

Answer 5

I'm expanding #Markus answer, because my case is i'm sending JSON string, so i need to added some escape, these are my function :
note :
the exception reference from w3schools. https://www.w3schools.com/tags/ref_urlencode.asp
- (NSString*)convertStringToHTMLEscape:(NSString*)stringContent
{
stringContent = [stringContent stringByReplacingOccurrencesOfString:#"{" withString:#"%7B"];
stringContent = [stringContent stringByReplacingOccurrencesOfString:#"}" withString:#"%7D"];
stringContent = [stringContent stringByReplacingOccurrencesOfString:#"[" withString:#"%5B"];
stringContent = [stringContent stringByReplacingOccurrencesOfString:#"]" withString:#"%5D"];
stringContent = [stringContent stringByReplacingOccurrencesOfString:#" " withString:#"%20"];
stringContent = [stringContent stringByReplacingOccurrencesOfString:#"\"" withString:#"%22"];
stringContent = [stringContent stringByReplacingOccurrencesOfString:#"\\" withString:#"%5C"];
stringContent = [stringContent stringByReplacingOccurrencesOfString:#"/" withString:#"%2F"];
return stringContent;
}

Answer 6

Assuming the character encoding of the email supports Unicode - say UTF-8 - could you not just find and replace the occurrences of <, >, and & with &lt, &gt, and &?