Converting HTML text into plain text using Objective-C - html

Question

I have huge NSString with HTML text inside. The length of this string is more then 3.500.000 characters. How can i convert this HTML text to NSString with plain text inside. I was using scanner , but it works too slowly. Any idea ?

Answer 1

It depends what iOS version you are targeting. Since iOS7 there is a built-in method that will not only strip the HTML tags, but also put the formatting to the string:
Xcode 9/Swift 4
if let htmlStringData = htmlString.data(using: .utf8), let attributedString = try? NSAttributedString(data: htmlStringData, options: [.documentType : NSAttributedString.DocumentType.html], documentAttributes: nil) {
print(attributedString)
}
You can even create an extension like this:
extension String {
var htmlToAttributedString: NSAttributedString? {
guard let data = self.data(using: .utf8) else {
return nil
}
do {
return try NSAttributedString(data: data, options: [.documentType : NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil)
} catch {
print("Cannot convert html string to attributed string: \(error)")
return nil
}
}
}
Note that this sample code is using UTF8 encoding. You can even create a function instead of computed property and add the encoding as a parameter.
Swift 3
let attributedString = try NSAttributedString(data: htmlString.dataUsingEncoding(NSUTF8StringEncoding)!,
options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
documentAttributes: nil)
Objective-C
[[NSAttributedString alloc] initWithData:[htmlString dataUsingEncoding:NSUTF8StringEncoding] options:#{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType, NSCharacterEncodingDocumentAttribute: [NSNumber numberWithInt:NSUTF8StringEncoding]} documentAttributes:nil error:nil];
If you just need to remove everything between < and > (dirty way!!!), which might be problematic if you have these characters in the string, use this:
- (NSString *)stringByStrippingHTML {
NSRange r;
NSString *s = [[self copy] autorelease];
while ((r = [s rangeOfString:#"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound)
s = [s stringByReplacingCharactersInRange:r withString:#""];
return s;
}

Answer 2

I resolve my question with scanner, but i use it not for all the text. I use it for every 10.000 text part, before i concatenate all parts together. My code below
-(NSString *)convertHTML:(NSString *)html {
NSScanner *myScanner;
NSString *text = nil;
myScanner = [NSScanner scannerWithString:html];
while ([myScanner isAtEnd] == NO) {
[myScanner scanUpToString:#"<" intoString:NULL] ;
[myScanner scanUpToString:#">" intoString:&text] ;
html = [html stringByReplacingOccurrencesOfString:[NSString stringWithFormat:#"%#>", text] withString:#""];
}
//
html = [html stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
return html;
}
Swift 4:
var htmlToString(html:String) -> String {
var htmlStr =html;
let scanner:Scanner = Scanner(string: htmlStr);
var text:NSString? = nil;
while scanner.isAtEnd == false {
scanner.scanUpTo("<", into: nil);
scanner.scanUpTo(">", into: &text);
htmlStr = htmlStr.replacingOccurrences(of: "\(text ?? "")>", with: "");
}
htmlStr = htmlStr.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines);
return htmlStr;
}

Answer 3

Objective C
+ (NSString*)textToHtml:(NSString*)htmlString
{
htmlString = [htmlString stringByReplacingOccurrencesOfString:#""" withString:#"\""];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"'" withString:#"'"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"&" withString:#"&"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#"<" withString:#"<"];
htmlString = [htmlString stringByReplacingOccurrencesOfString:#">" withString:#">"];
return htmlString;
}
Hope this helps!

Answer 4

For Swift Language ,
NSAttributedString(data:(htmlString as! String).dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true
)!, options:[NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType, NSCharacterEncodingDocumentAttribute: NSNumber(unsignedLong: NSUTF8StringEncoding)], documentAttributes: nil, error: nil)!

Answer 5

- (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;
}

Answer 6

Swift 4:
do {
let cleanString = try NSAttributedString(data: htmlContent.data(using: String.Encoding.utf8)!,
options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
documentAttributes: nil)
} catch {
print("Something went wrong")
}

Answer 7

It can be more generic by passing encoding type as parameter, but as example as this category:
#implementation NSString (CSExtension)
- (NSString *)htmlToText {
return [NSAttributedString.alloc
initWithData:[self dataUsingEncoding:NSUnicodeStringEncoding]
options:#{NSDocumentTypeDocumentOption: NSHTMLTextDocumentType}
documentAttributes:nil error:nil].string;
}
#end