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Decoding HTML Entities in Swift
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| // Very slightly adapted from http://stackoverflow.com/a/30141700/106244 | |
| // 99.99% Credit to Martin R! | |
| // Mapping from XML/HTML character entity reference to character | |
| // From http://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references | |
| private let characterEntities : [String: Character] = [ | |
| // XML predefined entities: | |
| """ : "\"", | |
| "&" : "&", | |
| "'" : "'", | |
| "<" : "<", | |
| ">" : ">", | |
| // HTML character entity references: | |
| " " : "\u{00A0}", | |
| "¡" : "\u{00A1}", | |
| "¢" : "\u{00A2}", | |
| "£" : "\u{00A3}", | |
| "¤" : "\u{00A4}", | |
| "¥" : "\u{00A5}", | |
| "¦" : "\u{00A6}", | |
| "§" : "\u{00A7}", | |
| "¨" : "\u{00A8}", | |
| "©" : "\u{00A9}", | |
| "ª" : "\u{00AA}", | |
| "«" : "\u{00AB}", | |
| "¬" : "\u{00AC}", | |
| "­" : "\u{00AD}", | |
| "®" : "\u{00AE}", | |
| "¯" : "\u{00AF}", | |
| "°" : "\u{00B0}", | |
| "±" : "\u{00B1}", | |
| "²" : "\u{00B2}", | |
| "³" : "\u{00B3}", | |
| "´" : "\u{00B4}", | |
| "µ" : "\u{00B5}", | |
| "¶" : "\u{00B6}", | |
| "·" : "\u{00B7}", | |
| "¸" : "\u{00B8}", | |
| "¹" : "\u{00B9}", | |
| "º" : "\u{00BA}", | |
| "»" : "\u{00BB}", | |
| "¼" : "\u{00BC}", | |
| "½" : "\u{00BD}", | |
| "¾" : "\u{00BE}", | |
| "¿" : "\u{00BF}", | |
| "À" : "\u{00C0}", | |
| "Á" : "\u{00C1}", | |
| "Â" : "\u{00C2}", | |
| "Ã" : "\u{00C3}", | |
| "Ä" : "\u{00C4}", | |
| "Å" : "\u{00C5}", | |
| "Æ" : "\u{00C6}", | |
| "Ç" : "\u{00C7}", | |
| "È" : "\u{00C8}", | |
| "É" : "\u{00C9}", | |
| "Ê" : "\u{00CA}", | |
| "Ë" : "\u{00CB}", | |
| "Ì" : "\u{00CC}", | |
| "Í" : "\u{00CD}", | |
| "Î" : "\u{00CE}", | |
| "Ï" : "\u{00CF}", | |
| "Ð" : "\u{00D0}", | |
| "Ñ" : "\u{00D1}", | |
| "Ò" : "\u{00D2}", | |
| "Ó" : "\u{00D3}", | |
| "Ô" : "\u{00D4}", | |
| "Õ" : "\u{00D5}", | |
| "Ö" : "\u{00D6}", | |
| "×" : "\u{00D7}", | |
| "Ø" : "\u{00D8}", | |
| "Ù" : "\u{00D9}", | |
| "Ú" : "\u{00DA}", | |
| "Û" : "\u{00DB}", | |
| "Ü" : "\u{00DC}", | |
| "Ý" : "\u{00DD}", | |
| "Þ" : "\u{00DE}", | |
| "ß" : "\u{00DF}", | |
| "à" : "\u{00E0}", | |
| "á" : "\u{00E1}", | |
| "â" : "\u{00E2}", | |
| "ã" : "\u{00E3}", | |
| "ä" : "\u{00E4}", | |
| "å" : "\u{00E5}", | |
| "æ" : "\u{00E6}", | |
| "ç" : "\u{00E7}", | |
| "è" : "\u{00E8}", | |
| "é" : "\u{00E9}", | |
| "ê" : "\u{00EA}", | |
| "ë" : "\u{00EB}", | |
| "ì" : "\u{00EC}", | |
| "í" : "\u{00ED}", | |
| "î" : "\u{00EE}", | |
| "ï" : "\u{00EF}", | |
| "ð" : "\u{00F0}", | |
| "ñ" : "\u{00F1}", | |
| "ò" : "\u{00F2}", | |
| "ó" : "\u{00F3}", | |
| "ô" : "\u{00F4}", | |
| "õ" : "\u{00F5}", | |
| "ö" : "\u{00F6}", | |
| "÷" : "\u{00F7}", | |
| "ø" : "\u{00F8}", | |
| "ù" : "\u{00F9}", | |
| "ú" : "\u{00FA}", | |
| "û" : "\u{00FB}", | |
| "ü" : "\u{00FC}", | |
| "ý" : "\u{00FD}", | |
| "þ" : "\u{00FE}", | |
| "ÿ" : "\u{00FF}", | |
| "Œ" : "\u{0152}", | |
| "œ" : "\u{0153}", | |
| "Š" : "\u{0160}", | |
| "š" : "\u{0161}", | |
| "Ÿ" : "\u{0178}", | |
| "ƒ" : "\u{0192}", | |
| "ˆ" : "\u{02C6}", | |
| "˜" : "\u{02DC}", | |
| "Α" : "\u{0391}", | |
| "Β" : "\u{0392}", | |
| "Γ" : "\u{0393}", | |
| "Δ" : "\u{0394}", | |
| "Ε" : "\u{0395}", | |
| "Ζ" : "\u{0396}", | |
| "Η" : "\u{0397}", | |
| "Θ" : "\u{0398}", | |
| "Ι" : "\u{0399}", | |
| "Κ" : "\u{039A}", | |
| "Λ" : "\u{039B}", | |
| "Μ" : "\u{039C}", | |
| "Ν" : "\u{039D}", | |
| "Ξ" : "\u{039E}", | |
| "Ο" : "\u{039F}", | |
| "Π" : "\u{03A0}", | |
| "Ρ" : "\u{03A1}", | |
| "Σ" : "\u{03A3}", | |
| "Τ" : "\u{03A4}", | |
| "Υ" : "\u{03A5}", | |
| "Φ" : "\u{03A6}", | |
| "Χ" : "\u{03A7}", | |
| "Ψ" : "\u{03A8}", | |
| "Ω" : "\u{03A9}", | |
| "α" : "\u{03B1}", | |
| "β" : "\u{03B2}", | |
| "γ" : "\u{03B3}", | |
| "δ" : "\u{03B4}", | |
| "ε" : "\u{03B5}", | |
| "ζ" : "\u{03B6}", | |
| "η" : "\u{03B7}", | |
| "θ" : "\u{03B8}", | |
| "ι" : "\u{03B9}", | |
| "κ" : "\u{03BA}", | |
| "λ" : "\u{03BB}", | |
| "μ" : "\u{03BC}", | |
| "ν" : "\u{03BD}", | |
| "ξ" : "\u{03BE}", | |
| "ο" : "\u{03BF}", | |
| "π" : "\u{03C0}", | |
| "ρ" : "\u{03C1}", | |
| "ς" : "\u{03C2}", | |
| "σ" : "\u{03C3}", | |
| "τ" : "\u{03C4}", | |
| "υ" : "\u{03C5}", | |
| "φ" : "\u{03C6}", | |
| "χ" : "\u{03C7}", | |
| "ψ" : "\u{03C8}", | |
| "ω" : "\u{03C9}", | |
| "ϑ" : "\u{03D1}", | |
| "ϒ" : "\u{03D2}", | |
| "ϖ" : "\u{03D6}", | |
| " " : "\u{2002}", | |
| " " : "\u{2003}", | |
| " " : "\u{2009}", | |
| "‌" : "\u{200C}", | |
| "‍" : "\u{200D}", | |
| "‎" : "\u{200E}", | |
| "‏" : "\u{200F}", | |
| "–" : "\u{2013}", | |
| "—" : "\u{2014}", | |
| "‘" : "\u{2018}", | |
| "’" : "\u{2019}", | |
| "‚" : "\u{201A}", | |
| "“" : "\u{201C}", | |
| "”" : "\u{201D}", | |
| "„" : "\u{201E}", | |
| "†" : "\u{2020}", | |
| "‡" : "\u{2021}", | |
| "•" : "\u{2022}", | |
| "…" : "\u{2026}", | |
| "‰" : "\u{2030}", | |
| "′" : "\u{2032}", | |
| "″" : "\u{2033}", | |
| "‹" : "\u{2039}", | |
| "›" : "\u{203A}", | |
| "‾" : "\u{203E}", | |
| "⁄" : "\u{2044}", | |
| "€" : "\u{20AC}", | |
| "ℑ" : "\u{2111}", | |
| "℘" : "\u{2118}", | |
| "ℜ" : "\u{211C}", | |
| "™" : "\u{2122}", | |
| "ℵ" : "\u{2135}", | |
| "←" : "\u{2190}", | |
| "↑" : "\u{2191}", | |
| "→" : "\u{2192}", | |
| "↓" : "\u{2193}", | |
| "↔" : "\u{2194}", | |
| "↵" : "\u{21B5}", | |
| "⇐" : "\u{21D0}", | |
| "⇑" : "\u{21D1}", | |
| "⇒" : "\u{21D2}", | |
| "⇓" : "\u{21D3}", | |
| "⇔" : "\u{21D4}", | |
| "∀" : "\u{2200}", | |
| "∂" : "\u{2202}", | |
| "∃" : "\u{2203}", | |
| "∅" : "\u{2205}", | |
| "∇" : "\u{2207}", | |
| "∈" : "\u{2208}", | |
| "∉" : "\u{2209}", | |
| "∋" : "\u{220B}", | |
| "∏" : "\u{220F}", | |
| "∑" : "\u{2211}", | |
| "−" : "\u{2212}", | |
| "∗" : "\u{2217}", | |
| "√" : "\u{221A}", | |
| "∝" : "\u{221D}", | |
| "∞" : "\u{221E}", | |
| "∠" : "\u{2220}", | |
| "∧" : "\u{2227}", | |
| "∨" : "\u{2228}", | |
| "∩" : "\u{2229}", | |
| "∪" : "\u{222A}", | |
| "∫" : "\u{222B}", | |
| "∴" : "\u{2234}", | |
| "∼" : "\u{223C}", | |
| "≅" : "\u{2245}", | |
| "≈" : "\u{2248}", | |
| "≠" : "\u{2260}", | |
| "≡" : "\u{2261}", | |
| "≤" : "\u{2264}", | |
| "≥" : "\u{2265}", | |
| "⊂" : "\u{2282}", | |
| "⊃" : "\u{2283}", | |
| "⊄" : "\u{2284}", | |
| "⊆" : "\u{2286}", | |
| "⊇" : "\u{2287}", | |
| "⊕" : "\u{2295}", | |
| "⊗" : "\u{2297}", | |
| "⊥" : "\u{22A5}", | |
| "⋅" : "\u{22C5}", | |
| "⌈" : "\u{2308}", | |
| "⌉" : "\u{2309}", | |
| "⌊" : "\u{230A}", | |
| "⌋" : "\u{230B}", | |
| "⟨" : "\u{2329}", | |
| "⟩" : "\u{232A}", | |
| "◊" : "\u{25CA}", | |
| "♠" : "\u{2660}", | |
| "♣" : "\u{2663}", | |
| "♥" : "\u{2665}", | |
| "♦" : "\u{2666}", | |
| ] | |
| extension String { | |
| /// Returns a new string made by replacing in the `String` | |
| /// all HTML character entity references with the corresponding | |
| /// character. | |
| var stringByDecodingHTMLEntities: String { | |
| return decodeHTMLEntities().decodedString | |
| } | |
| /// Returns a tuple containing the string made by relpacing in the | |
| /// `String` all HTML character entity references with the corresponding | |
| /// character. Also returned is an array of offset information describing | |
| /// the location and length offsets for each replacement. This allows | |
| /// for the correct adjust any attributes that may be associated with | |
| /// with substrings within the `String` | |
| func decodeHTMLEntities() -> (decodedString: String, replacementOffsets: [(index: String.Index, offset: String.Index.Distance)]) { | |
| // ===== Utility functions ===== | |
| // Record the index offsets of each replacement | |
| // This allows anyone to correctly adjust any attributes that may be | |
| // associated with substrings within the string | |
| var replacementOffsets: [(index: String.Index, offset: String.Index.Distance)] = [] | |
| // Convert the number in the string to the corresponding | |
| // Unicode character, e.g. | |
| // decodeNumeric("64", 10) --> "@" | |
| // decodeNumeric("20ac", 16) --> "€" | |
| func decodeNumeric(string : String, base : Int32) -> Character? { | |
| let code = UInt32(strtoul(string, nil, base)) | |
| return Character(UnicodeScalar(code)) | |
| } | |
| // Decode the HTML character entity to the corresponding | |
| // Unicode character, return `nil` for invalid input. | |
| // decode("@") --> "@" | |
| // decode("€") --> "€" | |
| // decode("<") --> "<" | |
| // decode("&foo;") --> nil | |
| func decode(entity : String) -> Character? { | |
| if entity.hasPrefix("&#x") || entity.hasPrefix("&#X"){ | |
| return decodeNumeric(entity.substringFromIndex(advance(entity.startIndex, 3)), 16) | |
| } else if entity.hasPrefix("&#") { | |
| return decodeNumeric(entity.substringFromIndex(advance(entity.startIndex, 2)), 10) | |
| } else { | |
| return characterEntities[entity] | |
| } | |
| } | |
| // ===== Method starts here ===== | |
| var result = "" | |
| var position = startIndex | |
| // Find the next '&' and copy the characters preceding it to `result`: | |
| while let ampRange = self.rangeOfString("&", range: position ..< endIndex) { | |
| result.extend(self[position ..< ampRange.startIndex]) | |
| position = ampRange.startIndex | |
| // Find the next ';' and copy everything from '&' to ';' into `entity` | |
| if let semiRange = self.rangeOfString(";", range: position ..< endIndex) { | |
| let entity = self[position ..< semiRange.endIndex] | |
| if let decoded = decode(entity) { | |
| // Replace by decoded character: | |
| result.append(decoded) | |
| // Record offset | |
| let offset = (index: semiRange.endIndex, offset: 1 - distance(position, semiRange.endIndex)) | |
| replacementOffsets.append(offset) | |
| } else { | |
| // Invalid entity, copy verbatim: | |
| result.extend(entity) | |
| } | |
| position = semiRange.endIndex | |
| } else { | |
| // No matching ';'. | |
| break | |
| } | |
| } | |
| // Copy remaining characters to `result`: | |
| result.extend(self[position ..< endIndex]) | |
| // Return results | |
| return (decodedString: result, replacementOffsets: replacementOffsets) | |
| } | |
| } |
@marbetschar any links on how to use the example you linked to?
Swift 4 anyone? https://gist.github.com/nathanfjohnson/380b9f24c991a8970144e13ddd044d21 Many changes and updates to the original approach.
for swift 3 :-
extension String {
/// Returns a new string made by replacing in the `String`
/// all HTML character entity references with the corresponding
/// character.
var stringByDecodingHTMLEntities : String {
// ===== Utility functions =====
// Convert the number in the string to the corresponding
// Unicode character, e.g.
// decodeNumeric("64", 10) --> "@"
// decodeNumeric("20ac", 16) --> "€"
func decodeNumeric(_ string : String, base : Int) -> Character? {
guard let code = UInt32(string, radix: base),
let uniScalar = UnicodeScalar(code) else { return nil }
return Character(uniScalar)
}
// Decode the HTML character entity to the corresponding
// Unicode character, return `nil` for invalid input.
// decode("@") --> "@"
// decode("€") --> "€"
// decode("<") --> "<"
// decode("&foo;") --> nil
func decode(_ entity : String) -> Character? {
if entity.hasPrefix("&#x") || entity.hasPrefix("&#X"){
return decodeNumeric(entity.substring(with: entity.index(entity.startIndex, offsetBy: 3) ..< entity.index(entity.endIndex, offsetBy: -1)), base: 16)
} else if entity.hasPrefix("&#") {
return decodeNumeric(entity.substring(with: entity.index(entity.startIndex, offsetBy: 2) ..< entity.index(entity.endIndex, offsetBy: -1)), base: 10)
} else {
return characterEntities[entity]
}
}
// ===== Method starts here =====
var result = ""
var position = startIndex
// Find the next '&' and copy the characters preceding it to `result`:
while let ampRange = self.range(of: "&", range: position ..< endIndex) {
result.append(self[position ..< ampRange.lowerBound])
position = ampRange.lowerBound
// Find the next ';' and copy everything from '&' to ';' into `entity`
if let semiRange = self.range(of: ";", range: position ..< endIndex) {
let entity = self[position ..< semiRange.upperBound]
position = semiRange.upperBound
if let decoded = decode(entity) {
// Replace by decoded character:
result.append(decoded)
} else {
// Invalid entity, copy verbatim:
result.append(entity)
}
} else {
// No matching ';'.
break
}
}
// Copy remaining characters to `result`:
result.append(self[position ..< endIndex])
return result
}
}
Swift 5+
extension String {
/// Returns a new string made by replacing in the `String`
/// all HTML character entity references with the corresponding
/// character.
var stringByDecodingHTMLEntities : String {
// ===== Utility functions =====
// Convert the number in the string to the corresponding
// Unicode character, e.g.
// decodeNumeric("64", 10) --> "@"
// decodeNumeric("20ac", 16) --> "€"
func decodeNumeric(_ string : String, base : Int) -> Character? {
guard let code = UInt32(string, radix: base),
let uniScalar = UnicodeScalar(code) else { return nil }
return Character(uniScalar)
}
// Decode the HTML character entity to the corresponding
// Unicode character, return `nil` for invalid input.
// decode("@") --> "@"
// decode("€") --> "€"
// decode("<") --> "<"
// decode("&foo;") --> nil
func decode(_ entity : String) -> Character? {
if entity.hasPrefix("&#x") || entity.hasPrefix("&#X"){
return decodeNumeric(
String(entity[
entity.index(entity.startIndex, offsetBy: 3)
..< entity.index(entity.endIndex, offsetBy: -1)
]), base: 16
)
} else if entity.hasPrefix("&#") {
return decodeNumeric(
String(entity[
entity.index(entity.startIndex, offsetBy: 2)
..< entity.index(entity.endIndex, offsetBy: -1)
]), base: 10
)
} else {
return characterEntities[entity]
}
}
// ===== Method starts here =====
var result = ""
var position = startIndex
// Find the next '&' and copy the characters preceding it to `result`:
while let ampRange = self.range(of: "&", range: position ..< endIndex) {
result.append(String(self[position ..< ampRange.lowerBound]))
position = ampRange.lowerBound
// Find the next ';' and copy everything from '&' to ';' into `entity`
if let semiRange = self.range(of: ";", range: position ..< endIndex) {
let entity = String(self[position ..< semiRange.upperBound])
position = semiRange.upperBound
if let decoded = decode(entity) {
// Replace by decoded character:
result.append(decoded)
} else {
// Invalid entity, copy verbatim:
result.append(entity)
}
} else {
// No matching ';'.
break
}
}
// Copy remaining characters to `result`:
result.append(String(self[position ..< endIndex]))
return result
}
}
Swift 5.7+
With the Regex Literal support introduced in Swift 5.7, this process has gotten much simpler:
let test: String = "Insisting on > splitting on the first < date"
var cleanText: String = ""
// Matches an HTML entity encoding, such as `<` or ` `
let regex = /&[A-Za-z0-9]{2,};/
var lastIndex: String.Index = test.startIndex
let ranges: [Range<String.Index>] = test.ranges(of: regex)
for range: Range<String.Index> in ranges
{
if range.lowerBound > lastIndex
{
cleanText.append(String(test[lastIndex ..< range.lowerBound]))
}
let doomedText: String = String(test[range.lowerBound ..< range.upperBound])
if let newCharacter: Character = characterEntities[doomedText]
{
cleanText.append(newCharacter)
lastIndex = range.upperBound
}
else
{
lastIndex = range.lowerBound
}
}
if lastIndex < test.endIndex
{
cleanText.append(String(test[lastIndex ..< test.endIndex]))
}
Warning
I haven't really tested all the edge cases in the above snippet and I typed it on GitHub, so it may require tweaking. Still, it's way more streamlined than the older approach and the performance is phenomenal.
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some manual work needed to extend the above for Swift 3.