60

Say I have an NSMutableAttributedString .

The string has a varied mix of formatting throughout:

Here is an example:

This string is hell to change in iOS, it really sucks.

However, the font per se is not the font you want.

I want to:

for each and every character, change that character to a specific font (say, Avenir)

BUT,

for each and every character, keep the mix of other attributions (bold, italic, colors, etc etc) which was previously in place on that character.

How the hell do you do this?

Note:

if you trivially add an attribute "Avenir" over the whole range: it simply deletes all the other attribute ranges, you lose all formatting. Unfortunately, attributes are not, in fact "additive".

Improve this question
6
  • 1
    developer.apple.com/reference/foundation/… to remove the NSFontAttributeName. You can also use developer.apple.com/reference/foundation/nsattributedstring/… to enumerate and decide if the font is to be removed or not. Commented May 1, 2017 at 18:04
  • Why don't you simply get the string from your attributedString and create a new attributedString with the desired font stackoverflow.com/a/28132610/2303865 Commented May 2, 2017 at 1:39
  • 1
    You said remove all attributes Commented May 2, 2017 at 3:02
  • 3
    I see you changed your question, then unupvoted & downvoted my answer to your original question and finished up by writing your own answer and accepting it as the solution. Poor show. Commented Nov 2, 2017 at 11:38
  • Man, no offense, but your formatting sucks. You should remove some font attributes - pun intended. Commented Jan 7, 2018 at 21:17

9 Answers 9

Reset to default
106
+400

Since rmaddy's answer did not work for me (f.fontDescriptor.withFace(font.fontName) does not keep traits like bold), here is an updated Swift 4 version that also includes color updating:

extension NSMutableAttributedString { func setFontFace(font: UIFont, color: UIColor? = nil) { beginEditing() self.enumerateAttribute( .font, in: NSRange(location: 0, length: self.length) ) { (value, range, stop) in if let f = value as? UIFont, let newFontDescriptor = f.fontDescriptor .withFamily(font.familyName) .withSymbolicTraits(f.fontDescriptor.symbolicTraits) { let newFont = UIFont( descriptor: newFontDescriptor, size: font.pointSize ) removeAttribute(.font, range: range) addAttribute(.font, value: newFont, range: range) if let color = color { removeAttribute( .foregroundColor, range: range ) addAttribute( .foregroundColor, value: color, range: range ) } } } endEditing() } }

Or, if your mix-of-attributes does not include font,
then you don't need to remove old font:

let myFont: UIFont = .systemFont(ofSize: UIFont.systemFontSize); myAttributedText.addAttributes( [NSAttributedString.Key.font: myFont], range: NSRange(location: 0, length: myAttributedText.string.count));

Notes

The problem with f.fontDescriptor.withFace(font.fontName) is that it removes symbolic traits like italic, bold or compressed, since it will for some reason override those with default traits of that font face. Why this is so totally eludes me, it might even be an oversight on Apple's part; or it's "not a bug, but a feature", because we get the new font's traits for free.

So what we have to do is create a font descriptor that has the symbolic traits from the original font's font descriptor: .withSymbolicTraits(f.fontDescriptor.symbolicTraits). Props to rmaddy for the initial code on which I iterated.

I've already shipped this in a production app where we parse a HTML string via NSAttributedString.DocumentType.html and then change the font and color via the extension above. No problems so far.

Improve this answer
Sign up to request clarification or add additional context in comments.

16 Comments

It's f.fontDescriptor.withFamily(font.familyName).withSymbolicTraits(f.fontDescriptor.symbolicTraits) that was different in rmaddy's code. Compare the code in his edit history.
@Fattie Oh I was silently logged out for a time and totally missed your comments, sorry! Thanks for the bounty :) In the meantime, I've released the above snippet as part of a production app, so yes it does indeed work. I'll try and elaborate a bit in the post above.
understood @manmal thanks again. yes what a nightmare! in some apps you have to do things that iOS really "doesn't want to do" and this is an example of that.
I discovered a minor bug in this implementation. If any part of the string has NO font attribute, then it won't be replaced. So you need to add } else { addAttribute(.font, value: font, range: range) } after the inner if block. Same for color if you need that.
@JAHelia if you are using a font that is shipped with ios, you can check here whether there is bold available: iosfonts.com
|
11

Here is a much simpler implementation that keeps all attributes in place, including all font attributes except it allows you to change the font face.

Note that this only makes use of the font face (name) of the passed in font. The size is kept from the existing font. If you want to also change all of the existing font sizes to the new size, change f.pointSize to font.pointSize.

extension NSMutableAttributedString { func replaceFont(with font: UIFont) { beginEditing() self.enumerateAttribute(.font, in: NSRange(location: 0, length: self.length)) { (value, range, stop) in if let f = value as? UIFont { let ufd = f.fontDescriptor.withFamily(font.familyName).withSymbolicTraits(f.fontDescriptor.symbolicTraits)! let newFont = UIFont(descriptor: ufd, size: f.pointSize) removeAttribute(.font, range: range) addAttribute(.font, value: newFont, range: range) } } endEditing() } }

And to use it:

let someMutableAttributedString = ... // some attributed string with some font face you want to change someMutableAttributedString.replaceFont(with: UIFont.systemFont(ofSize: 12))
Improve this answer

3 Comments

Dude I fear this may not actually work. As someone else also reports below there is a problem w/ bold. It takes an incredibly long time to fully test this stuff, and, unfortunately, me and my merry men have not yet had a chance to fully investigate it, but some quick tests seemed to fail. :O There are so many factors involved it is a real nightmare; it could be our test was messed up. :O
I really could have sworn that I tested this with a bold font but sure enough it wasn't working in a playground with Xcode 9.2. I've update the creating of the font descriptor and it's now working as expected.
@LinusGeffarth Yes, manmal fixed my answer (and added support for a color). I've updated my answer by fixing that one line of code so it works in all conditions.
7

my two cents for OSX/AppKit>

extension NSAttributedString { // replacing font to all: func setFont(_ font: NSFont, range: NSRange? = nil)-> NSAttributedString { let mas = NSMutableAttributedString(attributedString: self) let range = range ?? NSMakeRange(0, self.length) mas.addAttributes([.font: font], range: range) return NSAttributedString(attributedString: mas) } // keeping font, but change size: func setFont(size: CGFloat, range: NSRange? = nil)-> NSAttributedString { let mas = NSMutableAttributedString(attributedString: self) let range = range ?? NSMakeRange(0, self.length) mas.enumerateAttribute(.font, in: range) { value, range, stop in if let font = value as? NSFont { let name = font.fontName let newFont = NSFont(name: name, size: size) mas.addAttributes([.font: newFont!], range: range) } } return NSAttributedString(attributedString: mas) }
Improve this answer

Comments

3

Obj-C version of @manmal's answer

@implementation NSMutableAttributedString (Additions) - (void)setFontFaceWithFont:(UIFont *)font color:(UIColor *)color { [self beginEditing]; [self enumerateAttribute:NSFontAttributeName inRange:NSMakeRange(0, self.length) options:0 usingBlock:^(id _Nullable value, NSRange range, BOOL * _Nonnull stop) { UIFont *oldFont = (UIFont *)value; UIFontDescriptor *newFontDescriptor = [[oldFont.fontDescriptor fontDescriptorWithFamily:font.familyName] fontDescriptorWithSymbolicTraits:oldFont.fontDescriptor.symbolicTraits]; UIFont *newFont = [UIFont fontWithDescriptor:newFontDescriptor size:font.pointSize]; if (newFont) { [self removeAttribute:NSFontAttributeName range:range]; [self addAttribute:NSFontAttributeName value:newFont range:range]; } if (color) { [self removeAttribute:NSForegroundColorAttributeName range:range]; [self addAttribute:NSForegroundColorAttributeName value:newFont range:range]; } }]; [self endEditing]; } @end
Improve this answer

Comments

1

Important -

rmaddy has invented an entirely new technique for this annoying problem in iOS.

The answer by manmal is the final perfected version.

Purely for the historical record here is roughly how you'd go about doing it the old days...

// carefully convert to "our" font - "re-doing" any other formatting. // change each section BY HAND. total PITA. func fixFontsInAttributedStringForUseInApp() { cachedAttributedString?.beginEditing() let rangeAll = NSRange(location: 0, length: cachedAttributedString!.length) var boldRanges: [NSRange] = [] var italicRanges: [NSRange] = [] var boldANDItalicRanges: [NSRange] = [] // WTF right ?! cachedAttributedString?.enumerateAttribute( NSFontAttributeName, in: rangeAll, options: .longestEffectiveRangeNotRequired) { value, range, stop in if let font = value as? UIFont { let bb: Bool = font.fontDescriptor.symbolicTraits.contains(.traitBold) let ii: Bool = font.fontDescriptor.symbolicTraits.contains(.traitItalic) // you have to carefully handle the "both" case......... if bb && ii { boldANDItalicRanges.append(range) } if bb && !ii { boldRanges.append(range) } if ii && !bb { italicRanges.append(range) } } } cachedAttributedString!.setAttributes([NSFontAttributeName: font_f], range: rangeAll) for r in boldANDItalicRanges { cachedAttributedString!.addAttribute(NSFontAttributeName, value: font_fBOTH, range: r) } for r in boldRanges { cachedAttributedString!.addAttribute(NSFontAttributeName, value: font_fb, range: r) } for r in italicRanges { cachedAttributedString!.addAttribute(NSFontAttributeName, value: font_fi, range: r) } cachedAttributedString?.endEditing() }

.

Footnote. Just for clarity on a related point. This sort of thing inevitably starts as a HTML string. Here's a note on how to convert a string that is html to an NSattributedString .... you will end up with nice attribute ranges (italic, bold etc) BUT the fonts will be fonts you don't want.

fileprivate extension String { func htmlAttributedString() -> NSAttributedString? { guard let data = self.data(using: String.Encoding.utf16, allowLossyConversion: false) else { return nil } guard let html = try? NSMutableAttributedString( data: data, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil) else { return nil } return html } }

.

Even that part of the job is non-trivial, it takes some time to process. In practice you have to background it to avoid flicker.

Improve this answer

2 Comments

I just saw your footnote.. as I mentioned in the (newly written) notes in my answer, I'm also using the extension to override properties of text loaded from HTML. I'm also backgrounding and even caching it because it's so expensive. In case you need this, here is a gist: gist.github.com/manmal/c11ef79e306ffab25251ed911b3b0e80
Definitely a huge PITA!
1

There is a tiny bug in the accepted answer causing the original font size to get lost. To fix this simply replace

font.pointSize

with

f.pointSize

This ensures that e.g. H1 and H2 headings have the correct size.

Improve this answer

Comments

1

Swift 5

This properly scales the font size, as other answers overwrite the font size, which may differ, like with sub, sup attribute

For iOS replace NSFont->UIFont and NSColor->UIColor

extension NSMutableAttributedString { func setFont(_ font: NSFont, textColor: NSColor? = nil) { guard let fontFamilyName = font.familyName else { return } beginEditing() enumerateAttribute(NSAttributedString.Key.font, in: NSMakeRange(0, length), options: []) { (value, range, stop) in if let oldFont = value as? NSFont { let descriptor = oldFont .fontDescriptor .withFamily(fontFamilyName) .withSymbolicTraits(oldFont.fontDescriptor.symbolicTraits) // Default font is always Helvetica 12 // See: https://developer.apple.com/documentation/foundation/nsattributedstring?language=objc let size = font.pointSize * (oldFont.pointSize / 12) let newFont = NSFont(descriptor: descriptor, size: size) ?? oldFont addAttribute(NSAttributedString.Key.font, value: newFont, range: range) } } if let textColor = textColor { addAttributes([NSAttributedString.Key.foregroundColor:textColor], range: NSRange(location: 0, length: length)) } endEditing() } } extension NSAttributedString { func settingFont(_ font: NSFont, textColor: NSColor? = nil) -> NSAttributedString { let ms = NSMutableAttributedString(attributedString: self) ms.setFont(font, textColor: textColor) return ms } }
Improve this answer

Comments

1

For what it's worth I thought I'd add a really simple answer.

 extension NSAttributedString { func updateStringSize(by change:Int) -> NSAttributedString { var string = NSMutableAttributedString(attributedString: self), mSize : Int = 0 string.beginEditing() string.enumerateAttributes(in: NSMakeRange(0, string.length)) { value, range, done in if let font = value[NSAttributedString.Key.font] as? UIFont { for key in font.fontDescriptor.fontAttributes.keys { if key == .size { mSize = (font.fontDescriptor.fontAttributes[key] as? Int ?? 0) + change // The following line returns a new font descriptor that’s the same as //the existing descriptor, but with the specified attributes taking precedence over the existing ones. let newDes = font.fontDescriptor.addingAttributes([.size:mSize]) string.removeAttribute(.font, range: range) string.addAttributes([.font:UIFont(descriptor: newDes, size: CGFloat(mSize))], range: range) } } } } string.endEditing() return string } }
Improve this answer

1 Comment

Cheers Adam, you know what I edited the answer for you to help with the code formatting, you'd missed the first and last lines! (The "code format" button is hard to find on these sites; and all it does is sort of move the text to the right so it's unclear if it's done or not.) Have a good one
-3

Would it be valid to let a UITextField do the work?

Like this, given attributedString and newfont:

let textField = UITextField() textField.attributedText = attributedString textField.font = newFont let resultAttributedString = textField.attributedText

Sorry, I was wrong, it keeps the "Character Attributes" like NSForegroundColorAttributeName, e.g. the colour, but not the UIFontDescriptorSymbolicTraits, which describe bold, italic, condensed, etc.

Those belong to the font and not the "Character Attributes". So if you change the font, you are changing the traits as well. Sorry, but my proposed solution does not work. The target font needs to have all traits available as the original font for this to work.

Improve this answer

3 Comments

I tried it only with one color attribute and it did work, so hope the others work as well, had no time to fully test it.
Sorry, I was wrong, it keeps the "Character Attributes" like NSForegroundColorAttributeName, e.g. the colour, but not the UIFontDescriptorSymbolicTraits, which describe bold, italic, condensed, etc. which belong to the font and not the "Character Attributes". So if you change the font, you are changing the traits as well. Sorry, but my proposed solution does not work. The target font needs to have all traits available as the original font for this to work.
Instead of adding an edit that states the answer is wrong, it would be better to delete the answer (or fix it if you can).

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.