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

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;
}