How do I decode HTML entities in Swift?

Question

I am pulling a JSON file from a site and one of the strings received is:

The Weeknd ‘King Of The Fall&         


        

Answer 1

Swift 3 version of @akashivskyy's extension,

extension String {
    init(htmlEncodedString: String) {
        self.init()
        guard let encodedData = htmlEncodedString.data(using: .utf8) else {
            self = htmlEncodedString
            return
        }

        let attributedOptions: [String : Any] = [
            NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
            NSCharacterEncodingDocumentAttribute: String.Encoding.utf8.rawValue
        ]

        do {
            let attributedString = try NSAttributedString(data: encodedData, options: attributedOptions, documentAttributes: nil)
            self = attributedString.string
        } catch {
            print("Error: \(error)")
            self = htmlEncodedString
        }
    }
}

Answer 2

This would be my approach. You could add the entities dictionary from https://gist.github.com/mwaterfall/25b4a6a06dc3309d9555 Michael Waterfall mentions.

extension String {
    func htmlDecoded()->String {

        guard (self != "") else { return self }

        var newStr = self

        let entities = [
            """    : "\"",
            "&"     : "&",
            "'"    : "'",
            "&lt;"      : "<",
            "&gt;"      : ">",
        ]

        for (name,value) in entities {
            newStr = newStr.stringByReplacingOccurrencesOfString(name, withString: value)
        }
        return newStr
    }
}

Examples used:

let encoded = "this is so "good""
let decoded = encoded.htmlDecoded() // "this is so "good""

OR

let encoded = "this is so "good"".htmlDecoded() // "this is so "good""

Answer 3

I was looking for a pure Swift 3.0 utility to escape to/unescape from HTML character references (i.e. for server-side Swift apps on both macOS and Linux) but didn't find any comprehensive solutions, so I wrote my own implementation: https://github.com/IBM-Swift/swift-html-entities

The package, HTMLEntities, works with HTML4 named character references as well as hex/dec numeric character references, and it will recognize special numeric character references per the W3 HTML5 spec (i.e. € should be unescaped as the Euro sign (unicode U+20AC) and NOT as the unicode character for U+0080, and certain ranges of numeric character references should be replaced with the replacement character U+FFFD when unescaping).

Usage example:

import HTMLEntities

// encode example
let html = "<script>alert(\"abc\")</script>"

print(html.htmlEscape())
// Prints ”&lt;script&gt;alert(&quot;abc&quot;)&lt;/script&gt;"

// decode example
let htmlencoded = "&lt;script&gt;alert(&quot;abc&quot;)&lt;/script&gt;"

print(htmlencoded.htmlUnescape())
// Prints ”<script>alert(\"abc\")</script>"

And for OP's example:

print("The Weeknd ‘King Of The Fall’ [Video Premiere] | @TheWeeknd | #SoPhi ".htmlUnescape())
// prints "The Weeknd ‘King Of The Fall’ [Video Premiere] | @TheWeeknd | #SoPhi "

Edit: HTMLEntities now supports HTML5 named character references as of version 2.0.0. Spec-compliant parsing is also implemented.

Answer 4

Swift 4:

The total solution that finally worked for me with HTML code and newline characters and single quotes

extension String {
    var htmlDecoded: String {
        let decoded = try? NSAttributedString(data: Data(utf8), options: [
            .documentType: NSAttributedString.DocumentType.html,
            .characterEncoding: String.Encoding.utf8.rawValue
            ], documentAttributes: nil).string

        return decoded ?? self
    }
}

Usage:

let yourStringEncoded = yourStringWithHtmlcode.htmlDecoded

I then had to apply some more filters to get rid of single quotes (for example, don't, hasn't, It's, etc.), and new line characters like \n:

var yourNewString = String(yourStringEncoded.filter { !"\n\t\r".contains($0) })
yourNewString = yourNewString.replacingOccurrences(of: "\'", with: "", options: NSString.CompareOptions.literal, range: nil)

Answer 5

Updated answer working on Swift 3

extension String {
    init?(htmlEncodedString: String) {
        let encodedData = htmlEncodedString.data(using: String.Encoding.utf8)!
        let attributedOptions = [ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType]

        guard let attributedString = try? NSAttributedString(data: encodedData, options: attributedOptions, documentAttributes: nil) else {
            return nil
        }
        self.init(attributedString.string)
   }