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

There isn't an NSString method that does that. You'll have to write your own function that does string replacements. It is sufficient to do the following replacements:

• '&' => "&"
• '"' => """
• '\'' => "'"
• '>' => ">"
• '<' => "&lt;"

Something like this should do (haven't tried):

[[[[[myStr stringByReplacingOccurrencesOfString: @"&" withString: @"&"]
 stringByReplacingOccurrencesOfString: @"\"" withString: @"""]
 stringByReplacingOccurrencesOfString: @"'" withString: @"'"]
 stringByReplacingOccurrencesOfString: @">" withString: @">"]
 stringByReplacingOccurrencesOfString: @"<" withString: @"&lt;"];

Answer 2

I took Mike's work and turn it into a category for NSMutableString and NSString

Make a Category for NSMutableString with:

- (NSMutableString *)xmlSimpleUnescape
{
    [self replaceOccurrencesOfString:@"&"  withString:@"&"  options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@""" withString:@"\"" options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@"'" withString:@"'"  options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@"'"  withString:@"'"  options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@"’" withString:@"'"  options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@"–" withString:@"-"  options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@">"   withString:@">"  options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@"&lt;"   withString:@"<"  options:NSLiteralSearch range:NSMakeRange(0, [self length])];

    return self;
}

- (NSMutableString *)xmlSimpleEscape
{
    [self replaceOccurrencesOfString:@"&"  withString:@"&amp;"  options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@"\"" withString:@"&quot;" options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@"'"  withString:@"&#x27;" options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@">"  withString:@"&gt;"   options:NSLiteralSearch range:NSMakeRange(0, [self length])];
    [self replaceOccurrencesOfString:@"<"  withString:@"&lt;"   options:NSLiteralSearch range:NSMakeRange(0, [self length])];

    return self;
}

Make a Category for NSString with:

- (NSString *)xmlSimpleUnescapeString
{
    NSMutableString *unescapeStr = [NSMutableString stringWithString:self];

    return [unescapeStr xmlSimpleUnescape];
}


- (NSString *)xmlSimpleEscapeString
{
    NSMutableString *escapeStr = [NSMutableString stringWithString:self];

    return [escapeStr xmlSimpleEscape];
}

* A Swift 2.0 Version *

The Objective-C version is a little more efficient as it does mutable operations on the string. However, this is a swift way to do simple escaping:

extension String
{
    typealias SimpleToFromRepalceList = [(fromSubString:String,toSubString:String)]

    // See http://stackoverflow.com/questions/24200888/any-way-to-replace-characters-on-swift-string
    //
    func simpleReplace( mapList:SimpleToFromRepalceList ) -> String
    {
        var string = self

        for (fromStr, toStr) in mapList {
            let separatedList = string.componentsSeparatedByString(fromStr)
            if separatedList.count > 1 {
                string = separatedList.joinWithSeparator(toStr)
            }
        }

        return string
    }

    func xmlSimpleUnescape() -> String
    {
        let mapList : SimpleToFromRepalceList = [
            ("&",  "&"),
            (""", "\""),
            ("'", "'"),
            ("'",  "'"),
            ("’", "'"),
            ("–", "-"),
            (">",   ">"),
            ("&lt;",   "<")]

        return self.simpleReplace(mapList)
    }

    func xmlSimpleEscape() -> String
    {
        let mapList : SimpleToFromRepalceList = [
            ("&",  "&amp;"),
            ("\"", "&quot;"),
            ("'",  "&#x27;"),
            (">",  "&gt;"),
            ("<",  "&lt;")]

        return self.simpleReplace(mapList)
    }
}

I could have used the NSString bridging capabilities to write something very similar to the NSString version, but I decided to do it more swifty.

Answer 3

I use Google Toolbox for Mac (works on iPhone). In particular, see the additions to NSString in GTMNSString+HTML.h and GTMNSString+XML.h.

Answer 4

For URL encoding:

NSString * encodedString = [originalString
      stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding];

See Apple's NSString documentation for more info.

For HTML encoding:

Check out CFXMLCreateStringByEscapingEntities, which is part of the Core Foundation XML library, but should still do the trick.

Answer 5

the samets's routine forgot the hex digit. Here's the routine I came up with that works:

- (NSString*)convertEntities:(NSString*)string
{

NSString    *returnStr = nil;

    if( string )
    {
        returnStr = [ string stringByReplacingOccurrencesOfString:@"&" withString: @"&"  ];

        returnStr = [ returnStr stringByReplacingOccurrencesOfString:@""" withString:@"\""  ];

        returnStr = [ returnStr stringByReplacingOccurrencesOfString:@"'" withString:@"'"  ];

        returnStr = [ returnStr stringByReplacingOccurrencesOfString:@"9" withString:@"'"  ];

        returnStr = [ returnStr stringByReplacingOccurrencesOfString:@"’" withString:@"'"  ];

        returnStr = [ returnStr stringByReplacingOccurrencesOfString:@"–" withString:@"'"  ];

        returnStr = [ returnStr stringByReplacingOccurrencesOfString:@">" withString:@">"  ];

        returnStr = [ returnStr stringByReplacingOccurrencesOfString:@"&lt;" withString:@"<"  ];

        returnStr = [ [ NSString alloc ] initWithString:returnStr ];
    }

    return returnStr;
}

Answer 6

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 = @"&quot;";
    }
    else if (c == '\'')
    {
      replaceWithStr = @"&#x27;";
    }
    else if (c == '<')
    {
      replaceWithStr = @"&lt;";
    }
    else if (c == '>')
    {
      replaceWithStr = @"&gt;";
    }
    else if (c == '&')
    {
      replaceWithStr = @"&amp;";
    }

    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 "<foo/>", use "<foo />" instead
    return [NSString stringWithFormat:@"<%@ />", tagname];
  } else {
    NSString *escapedValue = [self xmlSimpleEscape:value];
    return [NSString stringWithFormat:@"<%@>%@</%@>", tagname, escapedValue, tagname];    
  }
}

Answer 7

If you can use NSXMLNode (on OS X) Here is the trick:

NSString *string = @"test<me>"
NSXMLNode *textNode = [NSXMLNode textWithStringValue:string];
NSString *escapedString = [textNode.XMLString];

Answer 8

Here is my swift category for html encoding/decoding:

extension String
{
    static let htmlEscapedDictionary = [
        "&": "&",
        """ : "\"",
        "'" : "'",
        "9" : "'",
        "’" : "'",
        "–" : "'",
        ">" : ">",
        "&lt;" : "<"]

    var escapedHtmlString : String {
        var newString = "\(self)"

        for (key, value) in String.htmlEscapedDictionary {
            newString.replace(value, withString: key)
        }
        return newString
    }

    var unescapedHtmlString : String {
        let encodedData = self.dataUsingEncoding(NSUTF8StringEncoding)!
        let attributedOptions : [String: AnyObject] = [
            NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
            NSCharacterEncodingDocumentAttribute: NSUTF8StringEncoding
        ]
        let attributedString = NSAttributedString(data: encodedData, options: attributedOptions, documentAttributes: nil, error: nil)!
        return attributedString.string
    }

    mutating func replace(originalString:String, withString newString:String)
    {
        let replacedString = self.stringByReplacingOccurrencesOfString(originalString, withString: newString, options: nil, range: nil)
        self = replacedString
    }
}

I guess a reverse of htmlEscapedDictionary could've been used as well in unescapedHtmlString

Note: As MarkBau pointed out in the comment below: Since Swift does not guarantee the order of dictionaries, make sure to replace & first.

Answer 9

I am not copletely sure if it will work in all cases, but may be it's easier to surround your text with CDATA:

<xmltag><![CDATA[some <b>long</b> <i>xml</i> text]]></xmltag>

what is CDATA: What does <![CDATA[]]> in XML mean?

Answer 10

I put together a quick example project using Mike and Tod's answers here.

Makes the encoding/unencoding dead simple:

NSString *html = @"<p>This \"paragraph\" contains quoted & 'single' quoted stuff.</p>";
NSLog(@"Original String: %@", html);

NSString *escapedHTML = [html xmlSimpleEscapeString];
NSLog(@"Escaped String: %@", escapedHTML);

NSString *unescapedHTML = [escapedHTML xmlSimpleUnescapeString];
NSLog(@"Unescaped String: %@", unescapedHTML);

Answer 11

Swift 4

extension String {
    var xmlEscaped: String {
        return replacingOccurrences(of: "&", with: "&")
            .replacingOccurrences(of: "\"", with: """)
            .replacingOccurrences(of: "'", with: "'")
            .replacingOccurrences(of: ">", with: ">")
            .replacingOccurrences(of: "<", with: "&lt;")
    }
}

Answer 12

This easiest solution is to create a category as below:

Here’s the category’s header file:

#import <Foundation/Foundation.h>
@interface NSString (URLEncoding)
-(NSString *)urlEncodeUsingEncoding:(NSStringEncoding)encoding;
@end

And here’s the implementation:

#import "NSString+URLEncoding.h"
@implementation NSString (URLEncoding)
-(NSString *)urlEncodeUsingEncoding:(NSStringEncoding)encoding {
    return (NSString *)CFURLCreateStringByAddingPercentEscapes(NULL,
               (CFStringRef)self,
               NULL,
               (CFStringRef)@"!*'\"();:@&=+$,/?%#[]% ",
               CFStringConvertNSStringEncodingToEncoding(encoding));
}
@end

And now we can simply do this:

NSString *raw = @"hell & brimstone + earthly/delight";
NSString *url = [NSString stringWithFormat:@"http://example.com/example?param=%@",
            [raw urlEncodeUsingEncoding:NSUTF8StringEncoding]];
NSLog(url);

The credits for this answer goes to the website below:-

http://madebymany.com/blog/url-encoding-an-nsstring-on-ios

Answer 13

Refer below answer:

NSString *content = global.strPrivacyPolicy;
content =  [[[[[content stringByReplacingOccurrencesOfString: @"&" withString: @"&"]
stringByReplacingOccurrencesOfString:@"""  withString:@"\" "]
stringByReplacingOccurrencesOfString: @"'"  withString:@"'"]
stringByReplacingOccurrencesOfString: @">" withString: @">"]
stringByReplacingOccurrencesOfString:  @"&lt;" withString:@"<"];
[_webViewPrivacy loadHTMLString:content baseURL:nil];

Answer 14

Use the message in the example below :

anyStringConverted = [anyString stringByReplacingOccurrencesOfString:@"\n" withString:@"<br>"]; 

This converts 'new line' command to corresponding html code. But to convert symbols, you have to write the corresponding html number. You can see the complete list of html numbers here at

http://www.ascii.cl/htmlcodes.htm

Answer 15

I found the only way that uses only built-in functions (not manual parsing) and covers all cases. Requires AppKit/UIKit in addition to Foundation. This is Swift but can easily be Objective-C:

func encodedForHTML() -> String {

    // make a plain attributed string and then use its HTML write functionality
    let attrStr = NSAttributedString(string: self)

    // by default, the document outputs a whole HTML element
    // warning: if default apple implementation changes, this may need to be tweaked
    let options: [NSAttributedString.DocumentAttributeKey: Any] = [
            .documentType: NSAttributedString.DocumentType.html,
            .excludedElements: [
                "html",
                "head",
                "meta",
                "title",
                "style",
                "p",
                "body",
                "font",
                "span"
            ]
    ]

    // generate data and turn into string
    let data = try! attrStr.data(from: NSRange(location: 0, length: attrStr.length), documentAttributes: options)
    let str = String(data: data, encoding: .utf8)!

    // remove <?xml line
    return str.components(separatedBy: .newlines).dropFirst().first!
}