Remove HTML Tags from an NSString on the iPhone

Question

There are a couple of different ways to remove HTML tags from an NSString in Cocoa.

One way is to render the string into an NSAttributedString and then grab the rendered text.

Another way is to use NSXMLDocument's -objectByApplyingXSLTString method to apply an XSLT transform that does it.

Unfortunately, the iPhone doesn't support NSAttributedString or NSXMLDocument. There are too many edge cases and malformed HTML documents for me to feel comfortable using regex or NSScanner. Does anyone have a solution to this?

One suggestion has been to simply look for opening and closing tag characters, this method won't work except for very trivial cases.

For example these cases (from the Perl Cookbook chapter on the same subject) would break this method:

<IMG SRC = "foo.gif" ALT = "A > B">

<!-- <A comment> -->

<script>if (a<b && a>c)</script>

<![INCLUDE CDATA [ >>>>>>>>>>>> ]]>

You could add a bit of logic to take quotes and apostrophes into account... CDATA would take a bit more work, but the whole point of HTML is that unknown tags can be ignored by the parser; if you treat ALL tags as unknown, then you should just get raw text. — Ben Gottlieb, Nov 10 '08 at 17:44
I'd like to comment that a good (but basic) regular expression will definitely not break at your examples. Certainly not if you can guarantee well formed XHTML. I know that you said you can't, but I wonder why ;-) — Jake, Oct 09 '09 at 12:54
There is **Good answer** for this question. [Flatten HTML using Objective c](http://rudis.net/content/2009/01/21/flatten-html-content-ie-strip-tags-cocoaobjective-c) — vipintj, Jul 09 '10 at 09:12
Even more unfortunately, the linked NSScanner example only works for trivial html. It fails for every test case I mentioned in my post. — lfalin, Jan 02 '13 at 14:35
Exactly why doesn't iOS support NSAttributedString for you? https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSAttributedString_Class/index.html — jasonjwwilliams, Feb 13 '15 at 02:18
@jasonjwwilliams I wrote this question in 2008. Support for NSAttributedString wasn't added to iOS until 3.2 (aka, the iPad release), which came out in April 2010. — lfalin, Feb 13 '15 at 16:59
@ifalin Apologies, I lost track of the 2008 date of the original post while reading. — jasonjwwilliams, Feb 17 '15 at 19:11
@jasonjwwilliams No worries. This is a problem with SO. You have answers to questions which often only apply as a "best practice" within a certain timeframe or API version. — lfalin, Feb 17 '15 at 19:18

score 313 · Accepted Answer · edited Jan 18 '13 at 21:39

313

A quick and "dirty" (removes everything between < and >) solution, works with iOS >= 3.2:

-(NSString *) stringByStrippingHTML {
  NSRange r;
  NSString *s = [[self copy] autorelease];
  while ((r = [s rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound)
    s = [s stringByReplacingCharactersInRange:r withString:@""];
  return s;
}

I have this declared as a category os NSString.

edited Jan 18 '13 at 21:39

dlinsin

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answered Feb 03 '11 at 13:56

m.kocikowski

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I'm a complete newb at iPhone development, but can I ask how you use this? – James Apr 26 '12 at 14:29
4

@James To use the method posted in the solution. You have to create a category for NSString. Look up "Objective-C Category" in Google. Then you add that method in the m file, and the prototype in the h file. When that is all set up, to use it all you have to do is have a string object (Example: NSString *myString = ...) and you call that method on your string object (NSString *strippedString = [myString stringByStrippingHTML];). – Roberto May 02 '12 at 17:40
3

+1 Great use for regular expressions, but does not cover lots of cases unfortunately. – matm Jun 18 '12 at 14:53
This code would break on Perl Cookbook examples 1, 3, and 4 in the question. – Aaron Brager Apr 18 '13 at 16:04
I am getting a NSString may not respond to stringByStrippingHTML with this. – Rick Jul 09 '13 at 19:01
3

Quick and dirty indeed.... This function causes a huge memory leak in my application... Well, in its defence, I am using large amounts of data.... – EZFrag Sep 09 '13 at 08:37
5

In my App this solution caused performance problems. I switched to a solution with NSScanner instead NSRegularExpressionSearch. Now the performance problems are gone – Carmen Sep 13 '13 at 13:13
2

It is very very very memory and time consuming. Only use this with small amounts of html! – ullstrm Apr 02 '14 at 13:11
Great idea, but insanely inefficient code. Instead use -[NSRegularExpression enumerateMatchesInString:] so that you only parse the regex once and don't rescan text you've already scanned. – Adlai Holler Jun 19 '15 at 16:37
When I try this I am getting this error : ` Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFString substringWithRange:]: Range {8587, 53} out of bounds; string length 8300'` – Rahul Jan 19 '16 at 13:34

score 30 · Answer 2 · edited Jan 25 '17 at 16:40

30

This NSString category uses the NSXMLParser to accurately remove any HTML tags from an NSString. This is a single .m and .h file that can be included into your project easily.

https://gist.github.com/leighmcculloch/1202238

You then strip html by doing the following:

Import the header:

#import "NSString_stripHtml.h"

And then call stripHtml:

NSString* mystring = @"<b>Hello</b> World!!";
NSString* stripped = [mystring stripHtml];
// stripped will be = Hello World!!

This also works with malformed HTML that technically isn't XML.

edited Jan 25 '17 at 16:40

Community

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answered Sep 08 '11 at 00:41

Leigh McCulloch

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Whilst the regular expression (as said by m.kocikowski) is quick and dirty, this is more robust. Example string: @"My test name\">html string". This answer returns: My test html string. Regular expression returns: My test name">html string. Whilst this isn't that common, it's just more robust. – DonnaLea Sep 08 '11 at 06:29
1

Except if you have a string like "S&P 500", it will strip everything after the ampersand and just return the string "S". – Joshua Gross Sep 08 '13 at 22:12

MANCHIKANTI KRISHNAKISHORE · Answer 3 · 2019-02-13T09:29:37.243

11

UITextView *textview= [[UITextView alloc]initWithFrame:CGRectMake(10, 130, 250, 170)];
NSString *str = @"This is <font color='red'>simple</font>";
[textview setValue:str forKey:@"contentToHTMLString"];
textview.textAlignment = NSTextAlignmentLeft;
textview.editable = NO;
textview.font = [UIFont fontWithName:@"vardana" size:20.0];
[UIView addSubview:textview];

work fine for me

edited Feb 13 '19 at 09:29

answered Jun 13 '13 at 07:08

MANCHIKANTI KRISHNAKISHORE

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I got encoding issue with this solution – KIDdAe Sep 23 '14 at 14:34
Probably the best solution, but it is useless for a UILabel :-( – Zeb Aug 28 '15 at 08:53

score 9 · Answer 4 · answered Oct 10 '13 at 09:00

You can use like below

-(void)myMethod
 {

 NSString* htmlStr = @"<some>html</string>";
 NSString* strWithoutFormatting = [self stringByStrippingHTML:htmlStr];

 }

 -(NSString *)stringByStrippingHTML:(NSString*)str
 {
   NSRange r;
   while ((r = [str rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location     != NSNotFound)
  {
     str = [str stringByReplacingCharactersInRange:r withString:@""];
 }
  return str;
 }

score 8 · Answer 5 · edited Sep 01 '17 at 01:06

8

use this

NSString *myregex = @"<[^>]*>"; //regex to remove any html tag

NSString *htmlString = @"<html>bla bla</html>";
NSString *stringWithoutHTML = [hstmString stringByReplacingOccurrencesOfRegex:myregex withString:@""];

don't forget to include this in your code : #import "RegexKitLite.h" here is the link to download this API : http://regexkit.sourceforge.net/#Downloads

edited Sep 01 '17 at 01:06

Johnny

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answered Nov 12 '10 at 11:15

Mohamed AHDIDOU

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score 7 · Answer 6 · answered Nov 10 '08 at 19:40

7

Take a look at NSXMLParser. It's a SAX-style parser. You should be able to use it to detect tags or other unwanted elements in the XML document and ignore them, capturing only pure text.

answered Nov 10 '08 at 19:40

Colin Barrett

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hpique · Answer 7 · 2014-03-13T15:01:10.250

Here's a more efficient solution than the accepted answer:

- (NSString*)hp_stringByRemovingTags
{
    static NSRegularExpression *regex = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        regex = [NSRegularExpression regularExpressionWithPattern:@"<[^>]+>" options:kNilOptions error:nil];
    });

    // Use reverse enumerator to delete characters without affecting indexes
    NSArray *matches =[regex matchesInString:self options:kNilOptions range:NSMakeRange(0, self.length)];
    NSEnumerator *enumerator = matches.reverseObjectEnumerator;

    NSTextCheckingResult *match = nil;
    NSMutableString *modifiedString = self.mutableCopy;
    while ((match = [enumerator nextObject]))
    {
        [modifiedString deleteCharactersInRange:match.range];
    }
    return modifiedString;
}

The above NSString category uses a regular expression to find all the matching tags, makes a copy of the original string and finally removes all the tags in place by iterating over them in reverse order. It's more efficient because:

The regular expression is initialised only once.
A single copy of the original string is used.

This performed well enough for me but a solution using NSScanner might be more efficient.

Like the accepted answer, this solution doesn't address all the border cases requested by @lfalin. Those would be require much more expensive parsing which the average use case most likely doesn't need.

score 5 · Answer 8 · answered May 26 '14 at 00:08

Without a loop (at least on our side) :

- (NSString *)removeHTML {

    static NSRegularExpression *regexp;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        regexp = [NSRegularExpression regularExpressionWithPattern:@"<[^>]+>" options:kNilOptions error:nil];
    });

    return [regexp stringByReplacingMatchesInString:self
                                            options:kNilOptions
                                              range:NSMakeRange(0, self.length)
                                       withTemplate:@""];
}

This should be the accepted answer. The current one is ridiculously wasteful. — Adlai Holler, Jun 19 '15 at 16:41

score 5 · Answer 9 · edited Mar 23 '15 at 10:01

5

NSAttributedString *str=[[NSAttributedString alloc] initWithData:[trimmedString dataUsingEncoding:NSUTF8StringEncoding] options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType, NSCharacterEncodingDocumentAttribute: [NSNumber numberWithInt:NSUTF8StringEncoding]} documentAttributes:nil error:nil];

edited Mar 23 '15 at 10:01

Robert

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answered Mar 23 '15 at 09:41

Pavan Sisode

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When we have the meta data with HTML tags and wants to apply that tags, that time we should apply the above code to achive the desire output. – Pavan Sisode Jun 13 '15 at 14:40

score 4 · Answer 10 · edited Jan 02 '12 at 10:52

4

#import "RegexKitLite.h"

string text = [html stringByReplacingOccurrencesOfRegex:@"<[^>]+>" withString:@""]

edited Jan 02 '12 at 10:52

sra

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answered Aug 12 '11 at 00:43

Jim Liu

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HTML isn't a regular language so you shouldn't be trying to parse/strip it with a regular expression. http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags – csaunders Dec 07 '11 at 18:34

score 3 · Answer 11 · answered Aug 24 '12 at 19:51

I've extended the answer by m.kocikowski and tried to make it a bit more efficient by using an NSMutableString. I've also structured it for use in a static Utils class (I know a Category is probably the best design though), and removed the autorelease so it compiles in an ARC project.

Included here in case anybody finds it useful.

.h

+ (NSString *)stringByStrippingHTML:(NSString *)inputString;

.m

+ (NSString *)stringByStrippingHTML:(NSString *)inputString 
{
  NSMutableString *outString;

  if (inputString)
  {
    outString = [[NSMutableString alloc] initWithString:inputString];

    if ([inputString length] > 0)
    {
      NSRange r;

      while ((r = [outString rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound)
      {
        [outString deleteCharactersInRange:r];
      }      
    }
  }

  return outString; 
}

This method is useful but , if i need to non-strip some tag such as link who i can update this method to fulfill this — wod, Mar 30 '13 at 08:06
@wod then just change the regex to `<(?>/?)(?!a).+?>` this will remove all tags excluding the opening and closing tags. — Ashoor, Jul 25 '13 at 20:48

score 3 · Answer 12 · edited Dec 27 '12 at 13:51

3

If you want to get the content without the html tags from the web page (HTML document) , then use this code inside the UIWebViewDidfinishLoading delegate method.

  NSString *myText = [webView stringByEvaluatingJavaScriptFromString:@"document.documentElement.textContent"];

edited Dec 27 '12 at 13:51

Hemang

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answered Oct 05 '09 at 10:13

Biranchi

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is being replaced by nothing...which is undesirable. – Nishant Sep 03 '13 at 23:03

score 2 · Answer 13 · answered Sep 23 '13 at 21:56

This is the modernization of m.kocikowski answer which removes whitespaces:

@implementation NSString (StripXMLTags)

- (NSString *)stripXMLTags
{
    NSRange r;
    NSString *s = [self copy];
    while ((r = [s rangeOfString:@"<[^>]+>\\s*" options:NSRegularExpressionSearch]).location != NSNotFound)
        s = [s stringByReplacingCharactersInRange:r withString:@""];
    return s;
}

@end

score 2 · Answer 14 · answered Nov 10 '08 at 04:56

2

I would imagine the safest way would just be to parse for <>s, no? Loop through the entire string, and copy anything not enclosed in <>s to a new string.

answered Nov 10 '08 at 04:56

Ben Gottlieb

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score 2 · Answer 15 · answered Nov 08 '15 at 12:44

2

Here's the swift version :

func stripHTMLFromString(string: String) -> String {
  var copy = string
  while let range = copy.rangeOfString("<[^>]+>", options: .RegularExpressionSearch) {
    copy = copy.stringByReplacingCharactersInRange(range, withString: "")
  }
  copy = copy.stringByReplacingOccurrencesOfString("&nbsp;", withString: " ")
  copy = copy.stringByReplacingOccurrencesOfString("&amp;", withString: "&")
  return copy
}

answered Nov 08 '15 at 12:44

JohnVanDijk

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Man, `stringByReplacingOccurrencesOfString` u use outside the cycle is percent encoding and should be fixed via a correct way. – Vyachaslav Gerchicov Nov 30 '16 at 12:06

score 1 · Answer 16 · answered Feb 18 '15 at 23:55

following is the accepted answer, but instead of category, it is simple helper method with string passed into it. (thank you m.kocikowski)

-(NSString *) stringByStrippingHTML:(NSString*)originalString {
    NSRange r;
    NSString *s = [originalString copy];
    while ((r = [s rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound)
        s = [s stringByReplacingCharactersInRange:r withString:@""];
    return s;
}

score 0 · Answer 17 · answered Jul 25 '13 at 20:43

Extending this more from m.kocikowski's and Dan J's answers with more explanation for newbies

1# First you have to create objective-c-categories to make the code useable in any class.

.h

@interface NSString (NAME_OF_CATEGORY)

- (NSString *)stringByStrippingHTML;

@end

.m

@implementation NSString (NAME_OF_CATEGORY)

- (NSString *)stringByStrippingHTML
{
NSMutableString *outString;
NSString *inputString = self;

if (inputString)
{
    outString = [[NSMutableString alloc] initWithString:inputString];

    if ([inputString length] > 0)
    {
        NSRange r;

        while ((r = [outString rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound)
        {
            [outString deleteCharactersInRange:r];
        }
    }
}

return outString;
}

@end

2# Then just import the .h file of the category class you've just created e.g.

#import "NSString+NAME_OF_CATEGORY.h"

3# Calling the Method.

NSString* sub = [result stringByStrippingHTML];
NSLog(@"%@", sub);

result is NSString I want to strip the tags from.

score 0 · Answer 18 · answered Apr 22 '15 at 18:56

I have following the accepted answer by m.kocikowski and modified is slightly to make use of an autoreleasepool to cleanup all of the temporary strings that are created by stringByReplacingCharactersInRange

In the comment for this method it states, /* Replace characters in range with the specified string, returning new string. */

So, depending on the length of your XML you may be creating a huge pile of new autorelease strings which are not cleaned up until the end of the next @autoreleasepool. If you are unsure when that may happen or if a user action could repeatedly trigger many calls to this method before then you can just wrap this up in an @autoreleasepool. These can even be nested and used within loops where possible.

Apple's reference on @autoreleasepool states this... "If you write a loop that creates many temporary objects. You may use an autorelease pool block inside the loop to dispose of those objects before the next iteration. Using an autorelease pool block in the loop helps to reduce the maximum memory footprint of the application." I have not used it in the loop, but at least this method cleans up after itself now.

- (NSString *) stringByStrippingHTML {
    NSString *retVal;
    @autoreleasepool {
        NSRange r;
        NSString *s = [[self copy] autorelease];
        while ((r = [s rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound) {
            s = [s stringByReplacingCharactersInRange:r withString:@""];
        }
        retVal = [s copy];
    } 
    // pool is drained, release s and all temp 
    // strings created by stringByReplacingCharactersInRange
    return retVal;
}

score 0 · Answer 19 · answered Jan 27 '16 at 10:35

Another one way:

Interface:

-(NSString *) stringByStrippingHTML:(NSString*)inputString;

Implementation

(NSString *) stringByStrippingHTML:(NSString*)inputString
{ 
NSAttributedString *attrString = [[NSAttributedString alloc] initWithData:[inputString dataUsingEncoding:NSUTF8StringEncoding] options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,NSCharacterEncodingDocumentAttribute: @(NSUTF8StringEncoding)} documentAttributes:nil error:nil];
NSString *str= [attrString string]; 

//you can add here replacements as your needs:
    [str stringByReplacingOccurrencesOfString:@"[" withString:@""];
    [str stringByReplacingOccurrencesOfString:@"]" withString:@""];
    [str stringByReplacingOccurrencesOfString:@"\n" withString:@""];

    return str;
}

Realization

cell.exampleClass.text = [self stringByStrippingHTML:[exampleJSONParsingArray valueForKey: @"key"]];

or simple

NSString *myClearStr = [self stringByStrippingHTML:rudeStr];

this method is removing html tags.but i want to parse html string.what to do — Krutarth Patel, Dec 28 '16 at 13:42

score 0 · Answer 20 · answered Oct 04 '10 at 12:17

0

If you are willing to use Three20 framework, it has a category on NSString that adds stringByRemovingHTMLTags method. See NSStringAdditions.h in Three20Core subproject.

answered Oct 04 '10 at 12:17

jarnoan

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For god's sake, don't use Three20 for anything. Most bloated and bad commented framework ever. – kompozer Jan 20 '12 at 15:45

score 0 · Answer 21 · answered Oct 05 '17 at 09:54

An updated answer for @m.kocikowski that works on recent iOS versions.

-(NSString *) stringByStrippingHTMLFromString:(NSString *)str {
NSRange range;
while ((range = [str rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound)
    str = [str stringByReplacingCharactersInRange:range withString:@""];
return str;

}

score -3 · Answer 22 · answered Nov 13 '08 at 18:02

-3

Here's a blog post that discusses a couple of libraries available for stripping HTML http://sugarmaplesoftware.com/25/strip-html-tags/ Note the comments where others solutions are offered.

answered Nov 13 '08 at 18:02

micco

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This is the exact set of comments that I linked to in my question as an example of what would not work. – lfalin Nov 14 '08 at 03:59

Remove HTML Tags from an NSString on the iPhone

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