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    lt IMG SRC    foo gif  ALT    A  gt  B  gt    lt  --  lt A comment gt  -- gt    lt script gt if  a lt b  amp  amp  a gt c  lt  script gt    lt   INCLUDE CDATA    gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt     gt

User · Answer

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

User · Answer

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

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NSAttributedString  str   NSAttributedString alloc  initWithData  trimmedString dataUsingEncoding NSUTF8StringEncoding  options   NSDocumentTypeDocumentAttribute  NSHTMLTextDocumentType  NSCharacterEncodingDocumentAttribute   NSNumber numberWithInt NSUTF8StringEncoding   documentAttributes nil error nil

User · Answer

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    lt    gt    gt   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

User · Answer

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

User · Answer

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   gt  0              NSRange r         while   r    outString rangeOfString    lt    gt    gt   options NSRegularExpressionSearch   location    NSNotFound                   outString deleteCharactersInRange r                              return outString

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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   gt  0                NSRange r           while   r    outString rangeOfString    lt    gt    gt   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

User · Answer

Here s a more efficient solution than the accepted answer   -  NSString  hp stringByRemovingTags       static NSRegularExpression  regex   nil      static dispatch once t onceToken      dispatch once  amp onceToken             regex    NSRegularExpression regularExpressionWithPattern    lt    gt    gt   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

User · Answer

NSAttributedString  str   NSAttributedString alloc  initWithData  trimmedString dataUsingEncoding NSUTF8StringEncoding  options   NSDocumentTypeDocumentAttribute  NSHTMLTextDocumentType  NSCharacterEncodingDocumentAttribute   NSNumber numberWithInt NSUTF8StringEncoding   documentAttributes nil error nil

User · Answer

use this   NSString  myregex      lt    gt    gt      regex to remove any html tag  NSString  htmlString      lt html gt bla bla lt  html gt    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

User · Answer

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

User · Answer

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

User · Answer

You can use like below  - void myMethod      NSString  htmlStr      lt some gt html lt  string gt     NSString  strWithoutFormatting    self stringByStrippingHTML htmlStr         - NSString   stringByStrippingHTML  NSString  str       NSRange r     while   r    str rangeOfString    lt    gt    gt   options NSRegularExpressionSearch   location        NSNotFound           str    str stringByReplacingCharactersInRange r withString            return str

User · Answer

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

User · Answer

UITextView  textview    UITextView alloc initWithFrame CGRectMake 10  130  250  170    NSString  str     This is  lt font color  red  gt simple lt  font gt     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

User · Answer

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

User · Answer

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

User · Answer

import  RegexKitLite h   string text    html stringByReplacingOccurrencesOfRegex    lt    gt    gt   withString

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A quick and  dirty   removes everything between  lt  and    solution  works with iOS    3 2    - NSString    stringByStrippingHTML     NSRange r    NSString  s     self copy  autorelease     while   r    s rangeOfString    lt    gt    gt   options NSRegularExpressionSearch   location    NSNotFound      s    s stringByReplacingCharactersInRange r withString         return s      I have this declared as a category os NSString

User · Answer

An updated answer for  m kocikowski that works on recent iOS versions   - NSString    stringByStrippingHTMLFromString  NSString   str   NSRange range  while   range    str rangeOfString    lt    gt    gt   options NSRegularExpressionSearch   location    NSNotFound      str    str stringByReplacingCharactersInRange range withString       return str

User · Answer

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

User · Answer

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

User · Answer

UITextView  textview    UITextView alloc initWithFrame CGRectMake 10  130  250  170    NSString  str     This is  lt font color  red  gt simple lt  font gt     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

User · Answer

An updated answer for  m kocikowski that works on recent iOS versions   - NSString    stringByStrippingHTMLFromString  NSString   str   NSRange range  while   range    str rangeOfString    lt    gt    gt   options NSRegularExpressionSearch   location    NSNotFound      str    str stringByReplacingCharactersInRange range withString       return str

User · Answer

You can use like below  - void myMethod      NSString  htmlStr      lt some gt html lt  string gt     NSString  strWithoutFormatting    self stringByStrippingHTML htmlStr         - NSString   stringByStrippingHTML  NSString  str       NSRange r     while   r    str rangeOfString    lt    gt    gt   options NSRegularExpressionSearch   location        NSNotFound           str    str stringByReplacingCharactersInRange r withString            return str

User · Answer

A quick and  dirty   removes everything between  lt  and    solution  works with iOS    3 2    - NSString    stringByStrippingHTML     NSRange r    NSString  s     self copy  autorelease     while   r    s rangeOfString    lt    gt    gt   options NSRegularExpressionSearch   location    NSNotFound      s    s stringByReplacingCharactersInRange r withString         return s      I have this declared as a category os NSString

User · Answer

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

User · Answer

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

User · Answer

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    lt    gt    gt   options NSRegularExpressionSearch   location    NSNotFound          s    s stringByReplacingCharactersInRange r withString           return s

User · Answer

Here s the swift version    func stripHTMLFromString string  String  - gt  String     var copy   string   while let range   copy rangeOfString   lt    gt    gt    options   RegularExpressionSearch        copy   copy stringByReplacingCharactersInRange range  withString            copy   copy stringByReplacingOccurrencesOfString   amp nbsp    withString         copy   copy stringByReplacingOccurrencesOfString   amp amp    withString    amp      return copy

User · Answer

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   gt  0              NSRange r         while   r    outString rangeOfString    lt    gt    gt   options NSRegularExpressionSearch   location    NSNotFound                   outString deleteCharactersInRange r                              return outString

User · Answer

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

User · Answer

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    lt    gt    gt   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

User · Answer

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

User · Answer

Here s a more efficient solution than the accepted answer   -  NSString  hp stringByRemovingTags       static NSRegularExpression  regex   nil      static dispatch once t onceToken      dispatch once  amp onceToken             regex    NSRegularExpression regularExpressionWithPattern    lt    gt    gt   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

User · Answer

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   gt  0                NSRange r           while   r    outString rangeOfString    lt    gt    gt   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

User · Answer

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    lt    gt    gt   s   options NSRegularExpressionSearch   location    NSNotFound          s    s stringByReplacingCharactersInRange r withString           return s      end

User · Answer

import  RegexKitLite h   string text    html stringByReplacingOccurrencesOfRegex    lt    gt    gt   withString

User · Answer

Without a loop  at least on our side     -  NSString   removeHTML        static NSRegularExpression  regexp      static dispatch once t onceToken      dispatch once  amp onceToken             regexp    NSRegularExpression regularExpressionWithPattern    lt    gt    gt   options kNilOptions error nil                return  regexp stringByReplacingMatchesInString self                                             options kNilOptions                                               range NSMakeRange 0  self length                                         withTemplate

User · Answer

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    lt    gt    gt   s   options NSRegularExpressionSearch   location    NSNotFound          s    s stringByReplacingCharactersInRange r withString           return s      end

User · Answer

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    lt    gt    gt   options NSRegularExpressionSearch   location    NSNotFound          s    s stringByReplacingCharactersInRange r withString           return s

User · Answer

Here s the swift version    func stripHTMLFromString string  String  - gt  String     var copy   string   while let range   copy rangeOfString   lt    gt    gt    options   RegularExpressionSearch        copy   copy stringByReplacingCharactersInRange range  withString            copy   copy stringByReplacingOccurrencesOfString   amp nbsp    withString         copy   copy stringByReplacingOccurrencesOfString   amp amp    withString    amp      return copy

User · Answer

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      lt b gt Hello lt  b gt  World     NSString  stripped    mystring stripHtml      stripped will be   Hello World     This also works with malformed HTML that technically isn t XML

User · Answer

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      lt b gt Hello lt  b gt  World     NSString  stripped    mystring stripHtml      stripped will be   Hello World     This also works with malformed HTML that technically isn t XML

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

use this   NSString  myregex      lt    gt    gt      regex to remove any html tag  NSString  htmlString      lt html gt bla bla lt  html gt    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

User · Answer

Without a loop  at least on our side     -  NSString   removeHTML        static NSRegularExpression  regexp      static dispatch once t onceToken      dispatch once  amp onceToken             regexp    NSRegularExpression regularExpressionWithPattern    lt    gt    gt   options kNilOptions error nil                return  regexp stringByReplacingMatchesInString self                                             options kNilOptions                                               range NSMakeRange 0  self length                                         withTemplate

User · Answer

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

[ios] Remove HTML Tags from an NSString on the iPhone

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