Swift- Change font on an HTML string that has its own Styles

The setAttributes will reset all the attributes from HTML. I wrote an extension method to avoid this:

Swift 4

public convenience init?(HTMLString html: String, font: UIFont? = nil) throws {
    let options : [NSAttributedString.DocumentReadingOptionKey : Any] =
        [NSAttributedString.DocumentReadingOptionKey.documentType: NSAttributedString.DocumentType.html,
         NSAttributedString.DocumentReadingOptionKey.characterEncoding: String.Encoding.utf8.rawValue]

    guard let data = html.data(using: .utf8, allowLossyConversion: true) else {
        throw NSError(domain: "Parse Error", code: 0, userInfo: nil)
    }

    if let font = font {
        guard let attr = try? NSMutableAttributedString(data: data, options: options, documentAttributes: nil) else {
            throw NSError(domain: "Parse Error", code: 0, userInfo: nil)
        }
        var attrs = attr.attributes(at: 0, effectiveRange: nil)
        attrs[NSAttributedStringKey.font] = font
        attr.setAttributes(attrs, range: NSRange(location: 0, length: attr.length))
        self.init(attributedString: attr)
    } else {
        try? self.init(data: data, options: options, documentAttributes: nil)
    }
}

Test sample:

let html = "
html text here
"
let font = UIFont.systemFont(ofSize: 16)

var attr = try NSMutableAttributedString(HTMLString: html, font: nil)
var attrs = attr?.attributes(at: 0, effectiveRange: nil)
attrs?[NSAttributedStringKey.font] as? UIFont
// print: <UICTFont: 0x7ff19fd0a530> font-family: "TimesNewRomanPS-BoldMT"; font-weight: bold; font-style: normal; font-size: 24.00pt

attr = try NSMutableAttributedString(HTMLString: html, font: font)
attrs = attr?.attributes(at: 0, effectiveRange: nil)
attrs?[NSAttributedStringKey.font] as? UIFont
// print: <UICTFont: 0x7f8c0cc04620> font-family: ".SFUIText"; font-weight: normal; font-style: normal; font-size: 16.00pt

NSAttributedString setting font size - swift

You are convert html to NSAttributedString?
You can append style to the string source.

example: https://stackoverflow.com/a/41519178/4368670

extension String {
    func htmlToAttributedString(fontName: String = "Chalkduster", fontSize: Float = 72) -> NSAttributedString? {
        let style = ""
        guard let data = (self + style).data(using: .utf8) else {
            return nil
        }
        return try? NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding:String.Encoding.utf8.rawValue], documentAttributes: nil)
    }
}

let html = "
content
"
lebal.attributedText = html.htmlToAttributedString()

result:

How to set custom font with regular and bold font while setting html string to label in swift 4?

This should help :

extension String {

func attributedString(withRegularFont regularFont: UIFont, andBoldFont boldFont: UIFont) -> NSMutableAttributedString {
    var attributedString = NSMutableAttributedString()
        guard let data = self.data(using: .utf8) else { return NSMutableAttributedString() }
        do {
            attributedString = try NSMutableAttributedString(data: data,
                                                             options: [.documentType: NSAttributedString.DocumentType.html,
                                                                       .characterEncoding:String.Encoding.utf8.rawValue],
                                                             documentAttributes: nil)
            let range = NSRange(location: 0, length: attributedString.length)
            attributedString.enumerateAttribute(NSAttributedString.Key.font, in: range, options: .longestEffectiveRangeNotRequired) { value, range, _ in
                let currentFont: UIFont         = value as! UIFont
                var replacementFont: UIFont?    = nil

                if currentFont.fontName.contains("bold") || currentFont.fontName.contains("Bold") {
                    replacementFont             =   boldFont
                } else {
                    replacementFont             =   regularFont
                }

                let replacementAttribute        =   [NSAttributedString.Key.font:replacementFont!]
                attributedString.addAttributes(replacementAttribute, range: range)
            }
        } catch let e {
            print(e.localizedDescription)
        }
       return attributedString
}
}

Parsing HTML into NSAttributedText - how to set font?

Figured it out. Bit of a bear, and maybe not the best answer.

This code will go through all the font changes. I know that it is using "Times New Roman" and "Times New Roman BoldMT" for the fonts.
But regardless, this will find the bold fonts and let me reset them. I can also reset the size while I'm at it.

I honestly hope/think there is a way to set this up at parse time, but I can't find it if there is.

    NSRange range = (NSRange){0,[str length]};
    [str enumerateAttribute:NSFontAttributeName inRange:range options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired usingBlock:^(id value, NSRange range, BOOL *stop) {
        UIFont* currentFont = value;
        UIFont *replacementFont = nil;

        if ([currentFont.fontName rangeOfString:@"bold" options:NSCaseInsensitiveSearch].location != NSNotFound) {
            replacementFont = [UIFont fontWithName:@"HelveticaNeue-CondensedBold" size:25.0f];
        } else {
            replacementFont = [UIFont fontWithName:@"HelveticaNeue-Thin" size:25.0f];
        }

        [str addAttribute:NSFontAttributeName value:replacementFont range:range];
    }];

Change just Font of AttributedText in Swift

You first need to understand the lingo Apple uses to describe a typeface:

• Helvetica is a family
• Helvetica Bold, Helvetica Italic, Helvetica Bold Italic, Helvetica Display etc. are faces
• Helvetica Bold, 12pt is a font

What you want is to replace the font family of an attributed string.

Swift 4

// Enumerate through all the font ranges
newAttributedString.enumerateAttribute(.font, in: NSMakeRange(0, newAttributedString.length), options: []) { value, range, stop in
    guard let currentFont = value as? UIFont else {
        return
    }

    // An NSFontDescriptor describes the attributes of a font: family name,
    // face name, point size, etc. Here we describe the replacement font as
    // coming from the "Hoefler Text" family
    let fontDescriptor = currentFont.fontDescriptor.addingAttributes([.family: "Hoefler Text"])

    // Ask the OS for an actual font that most closely matches the description above
    if let newFontDescriptor = fontDescriptor.matchingFontDescriptors(withMandatoryKeys: [.family]).first {
        let newFont = UIFont(descriptor: newFontDescriptor, size: currentFont.pointSize)
        newAttributedString.addAttributes([.font: newFont], range: range)
    }
}

label.attributedText = newAttributedString

Swift 3

let newAttributedString = NSMutableAttributedString(attributedString: label.attributedText)

// Enumerate through all the font ranges
newAttributedString.enumerateAttribute(NSFontAttributeName, in: NSMakeRange(0, newAttributedString.length), options: []) { value, range, stop in
    guard let currentFont = value as? UIFont else {
        return
    }

    // An NSFontDescriptor describes the attributes of a font: family name,
    // face name, point size, etc. Here we describe the replacement font as
    // coming from the "Hoefler Text" family
    let fontDescriptor = currentFont.fontDescriptor.addingAttributes([UIFontDescriptorFamilyAttribute: "Hoefler Text"])

    // Ask the OS for an actual font that most closely matches the description above
    if let newFontDescriptor = fontDescriptor.matchingFontDescriptors(withMandatoryKeys: [UIFontDescriptorFamilyAttribute]).first {
        let newFont = UIFont(descriptor: newFontDescriptor, size: currentFont.pointSize)
        newAttributedString.addAttributes([NSFontAttributeName: newFont], range: range)
    }
}

label.attributedText = newAttributedString

Original (San Francisco):

Replacement (Hoefler Text):

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