Convert HTML to Plain Text in Swift

Question

I'm working on a simple RSS Reader app as a beginner project in Xcode. I currently have it set up that it parses the feed, and places the title, pub date, description and content and displays it in a WebView.

I recently decided to show the description (or a truncated version of the content) in the TableView used to select a post. However, when doing so:

cell.textLabel?.text = item.title?.uppercaseString
cell.detailTextLabel?.text = item.itemDescription //.itemDescription is a String

It shows the raw HTML of the post.

I would like to know how to convert the HTML into plain text for just the TableView's detailed UILabel.

Thanks!

Answer 1

You can add this extension to convert your html code to a regular string:

edit/update:

Discussion The HTML importer should not be called from a background thread (that is, the options dictionary includes documentType with a value of html). It will try to synchronize with the main thread, fail, and time out. Calling it from the main thread works (but can still time out if the HTML contains references to external resources, which should be avoided at all costs). The HTML import mechanism is meant for implementing something like markdown (that is, text styles, colors, and so on), not for general HTML import.

Xcode 11.4 • Swift 5.2

extension Data {
    var html2AttributedString: NSAttributedString? {
        do {
            return try NSAttributedString(data: self, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil)
        } catch {
            print("error:", error)
            return  nil
        }
    }
    var html2String: String { html2AttributedString?.string ?? "" }
}

---

extension StringProtocol {
    var html2AttributedString: NSAttributedString? {
        Data(utf8).html2AttributedString
    }
    var html2String: String {
        html2AttributedString?.string ?? ""
    }
}

---

cell.detailTextLabel?.text = item.itemDescription.html2String

Answer 2

Swift 4, Xcode 9

extension String {
    
    var utfData: Data {
        return Data(utf8)
    }
    
    var attributedHtmlString: NSAttributedString? {
        
        do {
            return try NSAttributedString(data: utfData, options: [
              .documentType: NSAttributedString.DocumentType.html,
              .characterEncoding: String.Encoding.utf8.rawValue
            ], 
            documentAttributes: nil)
        } catch {
            print("Error:", error)
            return nil
        }
    }
}

extension UILabel {
   func setAttributedHtmlText(_ html: String) {
      if let attributedText = html.attributedHtmlString {
         self.attributedText = attributedText
      } 
   }
}

Answer 3

Here is my suggested answer. Instead of extension, if you want to put inside function.

func decodeString(encodedString:String) -> NSAttributedString?
    {
        let encodedData = encodedString.dataUsingEncoding(NSUTF8StringEncoding)!
        do {
            return try NSAttributedString(data: encodedData, options: [NSDocumentTypeDocumentAttribute:NSHTMLTextDocumentType,NSCharacterEncodingDocumentAttribute:NSUTF8StringEncoding], documentAttributes: nil)
        } catch let error as NSError {
            print(error.localizedDescription)
            return nil
        }
    }

And call that function and cast NSAttributedString to String

let attributedString = self.decodeString(encodedString)
let message = attributedString.string

Answer 4

Swift4.0 Extension

 extension String {
    var html2AttributedString: String? {
    guard let data = data(using: .utf8) else { return nil }
    do {
        return try NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil).string

    } catch let error as NSError {
        print(error.localizedDescription)
        return  nil
    }
  }
}

Answer 5

Please test with this code for the detailTextLabel:

var attrStr = NSAttributedString(
        data: item.itemDescription.dataUsingEncoding(NSUnicodeStringEncoding, allowLossyConversion: true),
        options: [ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
        documentAttributes: nil,
        error: nil)
cell.detailTextLabel?.text = attrStr

Answer 6

Try this solution in swift3

extension String{
    func convertHtml() -> NSAttributedString{
        guard let data = data(using: .utf8) else { return NSAttributedString() }
        do{
            return try NSAttributedString(data: data, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType, NSCharacterEncodingDocumentAttribute: String.Encoding.utf8.rawValue], documentAttributes: nil)
        }catch{
            return NSAttributedString()
        }
    }
}

To use

self.lblValDesc.attributedText = str_postdescription.convertHtml()

Answer 7

i have used Danboz answer, only changed it to return a simple String (not a rich text string):

static func htmlToText(encodedString:String) -> String?
{
    let encodedData = encodedString.dataUsingEncoding(NSUTF8StringEncoding)!
    do
    {
        return try NSAttributedString(data: encodedData, options: [NSDocumentTypeDocumentAttribute:NSHTMLTextDocumentType,NSCharacterEncodingDocumentAttribute:NSUTF8StringEncoding], documentAttributes: nil).string
    } catch let error as NSError {
        print(error.localizedDescription)
        return nil
    }
}

for me, it works like a charm, thanks Danboz

Answer 8

let content = givenString // html included string
let attrStr = try! NSAttributedString(data: content.data(using: String.Encoding.unicode, allowLossyConversion: true)!,options: [ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],documentAttributes: nil)
self.labelName.attributedText = attrStr    

Answer 9

Swift 5.*

Here's a compact solution based on string extension:

import UIKit

extension String {
    var attributedHtmlString: NSAttributedString? {
        try? NSAttributedString(
            data: Data(utf8),
            options: [
                .documentType: NSAttributedString.DocumentType.html,
                .characterEncoding: String.Encoding.utf8.rawValue
            ],
            documentAttributes: nil
        )
    }
}

Usage:

let html = "hello <br><br/> <b>world</b>"
if let attributedText = html.attributedHtmlString {
    print(attributedText.string) // "hello \n\nworld\n"
}

You can also keep the attributed string ofc, based on your necessities