Convert HTML to NSAttributedString in iOS
In iOS 7, UIKit added an initWithData:options:documentAttributes:error: method which can initialize an NSAttributedString using HTML, eg:
[[NSAttributedString alloc] initWithData:[htmlString dataUsingEncoding:NSUTF8StringEncoding]
options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
NSCharacterEncodingDocumentAttribute: @(NSUTF8StringEncoding)}
documentAttributes:nil error:nil];
In Swift:
let htmlData = NSString(string: details).data(using: String.Encoding.unicode.rawValue)
let options = [NSAttributedString.DocumentReadingOptionKey.documentType:
NSAttributedString.DocumentType.html]
let attributedString = try? NSMutableAttributedString(data: htmlData ?? Data(),
options: options,
documentAttributes: nil)
HTML to NSAttributedString and NSAttributedString to HTML
It's probably rounding errors in the round-trip. Try using integer point sizes (with pt instead of px)
Ok, looking at your console output, it's translating your px to pt, so maybe you can hack it by taking the HTML that comes from the conversion and changing pt back to px.
NSAttributedString: how to parse html tags and add attributes
Ok, I got the solution, maybe it will help anyone else.
Note, that my strings are strictly multi lined, so it's easy first split them, then add needed font and size to the parts, and then add paragraph styling.
I've played with order of parsing tags/styling fonts/styling paragraph, and at every case something was missed. If you don't need to separate line as multiline in strict order, just don't do mapping. Otherwise, you can miss breaking while styling or parsing tags.
descriptionLabel.attributedText = getAttributedDescriptionText(for: "Register and get <b>all</b>\n<b>rewards cards</b> of our partners\n<b>in one</b> universal <b>card</b>", fontDescription: "ProximaNova-Regular", fontSize: 15)
func getAttributedDescriptionText(for descriptionString: String, fontDescription: String, fontSize: Int) -> NSAttributedString? {
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.lineSpacing = 1.0
paragraphStyle.alignment = .center
paragraphStyle.minimumLineHeight = 18.0
let attributedString = NSMutableAttributedString()
let splits = descriptionString.components(separatedBy: "\n")
_ = splits.map { string in
let modifiedFont = String(format:"<span style=\"font-family: '\(fontDescription)'; font-size: \(fontSize)\">%@</span>", string)
let data = modifiedFont.data(using: String.Encoding.unicode, allowLossyConversion: true)
let attr = try? NSMutableAttributedString(
data: data ?? Data(),
options: [
.documentType: NSAttributedString.DocumentType.html,
.characterEncoding: String.Encoding.utf8.rawValue
],
documentAttributes: nil
)
attributedString.append(attr ?? NSMutableAttributedString())
if string != splits.last {
attributedString.append(NSAttributedString(string: "\n"))
}
}
attributedString.addAttribute(.paragraphStyle, value: paragraphStyle, range: NSRange(location: 0, length: attributedString.length))
return attributedString
}
NSAttributedString from HTML with Hyperlinks
I think you have error with your convertHTML() Method check this
let htmlString = "<html><p>If you would like to contact someone, you can email them at <a class=rvts10 href=\"mailto:some@one.com\">some@one.com</a></p></html>"
// you have to convert string to data
let data = Data(htmlString.utf8)
// then convert data to NSAttributedString with NSAttributedString.DocumentType.htm
if let attributedString = try? NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html], documentAttributes: nil) {
self.textView.attributedText = attributedString
}
Convert attributed string, to, simple tagged html
According to the documentation of enumerateAttribute:inRange:options:usingBlock:, especially the Discussion part which states:
If this method is sent to an instance of NSMutableAttributedString,
mutation (deletion, addition, or change) is allowed, as long as it is
within the range provided to the block; after a mutation, the
enumeration continues with the range immediately following the
processed range, after the length of the processed range is adjusted
for the mutation. (The enumerator basically assumes any change in
length occurs in the specified range.) For example, if block is called
with a range starting at location N, and the block deletes all the
characters in the supplied range, the next call will also pass N as
the index of the range.
In other words, in the closure/block, with the range, you can delete/replace characters there. The OS will put a marker on that end of the range. Once you did your modifications, it will compute the marker new range in order that the next iteration of the enumeration will start from that new marker.
So you don't have to keep all the ranges in an array and apply the changes afterwards by doing a backward replacement to not modify the range. Don't bother you with that, the methods does it already.
I'm not a Swift developper, I'm more an Objective-C one. So my Swift code may not respect all "Swift rules", and may be a little ugly (optionals, wrapping, etc badly done, if let not done, etc.)
Here is my solution:
func attrStrSimpleTag() -> Void {
let htmlStr = "<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01//EN\" \"http://www.w3.org/TR/html4/strict.dtd\"> <html> <head> <meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\"> <meta http-equiv=\"Content-Style-Type\" content=\"text/css\"> <title></title> <meta name=\"Generator\" content=\"Cocoa HTML Writer\"> <style type=\"text/css\"> p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px 'Some Font'} span.s1 {font-family: 'SomeFont-ItalicOrWhatever'; font-weight: normal; font-style: normal; font-size: 14.00pt} span.s2 {font-family: 'SomeFont-SemiboldItalic'; font-weight: bold; font-style: italic; font-size: 14.00pt} </style> </head> <body> <p class=\"p1\"><span class=\"s1\">So, </span><span class=\"s2\">here is</span><span class=\"s1\"> some</span> stuff</p> </body></html>"
let attr = try! NSMutableAttributedString.init(data: htmlStr.data(using: .utf8)!,
options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
documentAttributes: nil)
print("Attr: \(attr)")
attr.enumerateAttribute(NSFontAttributeName, in: NSRange.init(location: 0, length: attr.length), options: []) { (value, range, stop) in
if let font = value as? UIFont {
print("font found:\(font)")
let isBold = font.fontDescriptor.symbolicTraits.contains(.traitBold)
let isItalic = font.fontDescriptor.symbolicTraits.contains(.traitItalic)
let occurence = attr.attributedSubstring(from: range).string
let replacement = self.formattedString(initialString: occurence, bold: isBold, italic: isItalic)
attr.replaceCharacters(in: range, with: replacement)
}
};
let taggedString = attr.string
print("taggedString: \(taggedString)")
}
func formattedString(initialString:String, bold: Bool, italic: Bool) -> String {
var retString = initialString
if bold {
retString = "<b>".appending(retString)
retString.append("</b>")
}
if italic
{
retString = "<i>".appending(retString)
retString.append("</i>")
}
return retString
}
Output (for the last one, the other two prints are just for debug):
$> taggedString: So, <i><b>here is</b></i> some stuff
Edit:
Objective-C Version (quickly written, maybe some issue).
-(void)attrStrSimpleTag
{
NSString *htmlStr = @"<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01//EN\" \"http://www.w3.org/TR/html4/strict.dtd\"> <html> <head> <meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\"> <meta http-equiv=\"Content-Style-Type\" content=\"text/css\"> <title></title> <meta name=\"Generator\" content=\"Cocoa HTML Writer\"> <style type=\"text/css\"> p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px 'Some Font'} span.s1 {font-family: 'SomeFont-ItalicOrWhatever'; font-weight: normal; font-style: normal; font-size: 14.00pt} span.s2 {font-family: 'SomeFont-SemiboldItalic'; font-weight: bold; font-style: italic; font-size: 14.00pt} </style> </head> <body> <p class=\"p1\"><span class=\"s1\">So, </span><span class=\"s2\">here is</span><span class=\"s1\"> some</span> stuff</p> </body></html>";
NSMutableAttributedString *attr = [[NSMutableAttributedString alloc] initWithData:[htmlStr dataUsingEncoding:NSUTF8StringEncoding]
options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType}
documentAttributes:nil
error:nil];
NSLog(@"Attr: %@", attr);
[attr enumerateAttribute:NSFontAttributeName inRange:NSMakeRange(0, [attr length]) options:0 usingBlock:^(id _Nullable value, NSRange range, BOOL * _Nonnull stop) {
UIFont *font = (UIFont *)value;
NSLog(@"Font found: %@", font);
BOOL isBold = UIFontDescriptorTraitBold & [[font fontDescriptor] symbolicTraits];
BOOL isItalic = UIFontDescriptorTraitItalic & [[font fontDescriptor] symbolicTraits];
NSString *occurence = [[attr attributedSubstringFromRange:range] string];
NSString *replacement = [self formattedStringWithString:occurence isBold:isBold andItalic:isItalic];
[attr replaceCharactersInRange:range withString:replacement];
}];
NSString *taggedString = [attr string];
NSLog(@"taggedString: %@", taggedString);
}
-(NSString *)formattedStringWithString:(NSString *)string isBold:(BOOL)isBold andItalic:(BOOL)isItalic
{
NSString *retString = string;
if (isBold)
{
retString = [NSString stringWithFormat:@"<b>%@</b>", retString];
}
if (isItalic)
{
retString = [NSString stringWithFormat:@"<i>%@</i>", retString];
}
return retString;
}
Edit Jan. 2020:
Updated code with easier modifications and Swift 5, adding support for two new effects (underline/strikethrough).
// MARK: In one loop
extension NSMutableAttributedString {
func htmlSimpleTagString() -> String {
enumerateAttributes(in: fullRange(), options: []) { (attributes, range, pointeeStop) in
let occurence = self.attributedSubstring(from: range).string
var replacement: String = occurence
if let font = attributes[.font] as? UIFont {
replacement = self.font(initialString: replacement, fromFont: font)
}
if let underline = attributes[.underlineStyle] as? Int {
replacement = self.underline(text: replacement, fromStyle: underline)
}
if let striked = attributes[.strikethroughStyle] as? Int {
replacement = self.strikethrough(text: replacement, fromStyle: striked)
}
self.replaceCharacters(in: range, with: replacement)
}
return self.string
}
}
// MARK: In multiple loop
extension NSMutableAttributedString {
func htmlSimpleTagString(options: [NSAttributedString.Key]) -> String {
if options.contains(.underlineStyle) {
enumerateAttribute(.underlineStyle, in: fullRange(), options: []) { (value, range, pointeeStop) in
let occurence = self.attributedSubstring(from: range).string
guard let style = value as? Int else { return }
if NSUnderlineStyle(rawValue: style) == NSUnderlineStyle.styleSingle {
let replacement = self.underline(text: occurence, fromStyle: style)
self.replaceCharacters(in: range, with: replacement)
}
}
}
if options.contains(.strikethroughStyle) {
enumerateAttribute(.strikethroughStyle, in: fullRange(), options: []) { (value, range, pointeeStop) in
let occurence = self.attributedSubstring(from: range).string
guard let style = value as? Int else { return }
let replacement = self.strikethrough(text: occurence, fromStyle: style)
self.replaceCharacters(in: range, with: replacement)
}
}
if options.contains(.font) {
enumerateAttribute(.font, in: fullRange(), options: []) { (value, range, pointeeStop) in
let occurence = self.attributedSubstring(from: range).string
guard let font = value as? UIFont else { return }
let replacement = self.font(initialString: occurence, fromFont: font)
self.replaceCharacters(in: range, with: replacement)
}
}
return self.string
}
}
//MARK: Replacing
extension NSMutableAttributedString {
func font(initialString: String, fromFont font: UIFont) -> String {
let isBold = font.fontDescriptor.symbolicTraits.contains(.traitBold)
let isItalic = font.fontDescriptor.symbolicTraits.contains(.traitItalic)
var retString = initialString
if isBold {
retString = "<b>" + retString + "</b>"
}
if isItalic {
retString = "<i>" + retString + "</i>"
}
return retString
}
func underline(text: String, fromStyle style: Int) -> String {
return "<u>" + text + "</u>"
}
func strikethrough(text: String, fromStyle style: Int) -> String {
return "<s>" + text + "</s>"
}
}
//MARK: Utility
extension NSAttributedString {
func fullRange() -> NSRange {
return NSRange(location: 0, length: self.length)
}
}
Simple HTML to test with mixed tags: "This is <i>ITALIC</i> with some <b>BOLD</b> <b><i>BOLDandITALIC</b></i> <b>BOLD<u>UNDERLINEandBOLD</b>RESTUNDERLINE</u> in it."
The solutions brings two approaches: One doing one loop, the other doing multiple loops, but for mixed tags, the result could be strange. Check with the sample provided previously the different rendering.
Swift - Convert HTML text to Attributed String
I tried this solution with your html and worked fine:
let htmlText = "<medium><b><font color='#2f3744'>IPL Tamil Web Series Episode #3 | யாருடா Swetha ? | Tamil Comedy Web Series | Being Thamizhan</font></b></medium> has been succesfully scheduled on <medium><b><font color='#2f3744'>2018-05-23 08:51 PM</font></b></medium>"
let encodedData = htmlText.data(using: String.Encoding.utf8)!
var attributedString: NSAttributedString
do {
attributedString = try NSAttributedString(data: encodedData, options: [NSAttributedString.DocumentReadingOptionKey.documentType:NSAttributedString.DocumentType.html,NSAttributedString.DocumentReadingOptionKey.characterEncoding:NSNumber(value: String.Encoding.utf8.rawValue)], documentAttributes: nil)
} catch let error as NSError {
print(error.localizedDescription)
} catch {
print("error")
}
attributedString output:
IPL Tamil Web Series Episode #3 | யாருடா Swetha ? | Tamil Comedy Web Series | Being Thamizhan has been succesfully scheduled on 2018-05-23 08:45 PM
NSAttributedString to HTML string without CSS
I do not have the exact code I used to solve it, but I solved it by iterating the nsfontattributes and manually adding the supported html tags. Something like this in a NSAttributedString extension:
enumerateAttribute(NSFontAttributeName, inRange: NSMakeRange(0, length), options: NSAttributedStringEnumerationOptions(rawValue: 0)) { (value, range, stop) in
if let font = value as? UIFont {
var stringInRange = string.substringInRange(range)
if font.isBold {
stringInRange = "<b>\(stringInRange)</b>"
}
if font.isItalic {
stringInRange = "<i>\(stringInRange)</i>"
}
// ...
}
}
Convert NSAttributedString to HTML String
I used webView instead of textView to display attributed string.
NSString *strState = [webView stringByEvaluatingJavaScriptFromString:@"document.body.innerHTML"];
This method will return to you HTML string without CSS.
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