How to format attributed strings in swift?

Question

I'm working on a notification page where inputs are mostly come from a JSON file and I need to combine them with localized strings. This is how it should look:

As can be predicted colored parts come from the JSON file and rest of it comes from Localizable.strings. This is what comes from Localizable file:

"%@ has joined %@"

If I use String(format: String, [...]) I have a plain black text and I cant specify the parts needs to be colored.

I need the same feature for NSAttributedString but it doesn't have this method.

So how can I format attributed strings?

It depends on what kind of effects you want to apply, but the easiest way is is to use HTML tags on the localizaed value. — Larme
– Larme, Commented Sep 26, 2017 at 18:34
@Larme I want to change color and make bold the formatted parts, check the example screenshot. Does UILabel apply HTML tags automatically? — EfeHelvaci
– EfeHelvaci, Commented Sep 26, 2017 at 18:42
I checked the sample, but you may want more effects. You can init NSAttributedString from HTML Text (all tags are not translated, but just the bold/color are managed): stackoverflow.com/questions/39248092/… So adding <b> and others should do the trick. — Larme
– Larme, Commented Sep 26, 2017 at 18:43

casillas · Accepted Answer · 2017-09-26 18:34:59Z

3

Check following example:

var myMutableString = NSMutableAttributedString()

myMutableString = NSMutableAttributedString(string: "Your full label textString")

myMutableString.setAttributes([NSFontAttributeName : UIFont(name: "HelveticaNeue-Light", size: CGFloat(17.0))!
        , NSForegroundColorAttributeName : UIColor(red: 232 / 255.0, green: 117 / 255.0, blue: 40 / 255.0, alpha: 1.0)], range: NSRange(location:12,length:8)) // What ever range you want to give

yourLabel.attributedText = myMutableString

Or another way:

To change the colour of a length of text you need to know the start and end index of the coloured-to-be characters in the string e.g.

var main_string = "Hello World"
var string_to_color = "World"

var range = (main_string as NSString).rangeOfString(string_to_color)

Then you convert to attributed string and use 'add attribute' with NSForegroundColorAttributeName:

var attributedString = NSMutableAttributedString(string:main_string)
attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.redColor() , range: range)

answered Sep 26, 2017 at 18:34

casillas

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3 Comments

Larme Over a year ago

rangeOfString() returns the first range only. If both values of the placeholders (in "%@ has joined %@") are the same, it won't work.

Leo Dabus Over a year ago

rangeOfString have been renamed to range(of: String) since Swift 3

Larme Over a year ago

There is also an issue if you use "$1, $2", to place items (not all languages keep the same order). That's why on my project I used HTML Tags instead. But that's more for information than anything. Your solution could work.

iqra · Accepted Answer · 2021-04-09 18:24:22Z

My two localised strings:

"welcome message" = "%@ has joined %@";
"welcome message" = "انضم %@ إلى %@";

Results


extension String {

 func localisedAttributedString(_ replacements: CVarArg..., attributes: [NSAttributedString.Key : Any], replacementAttributes: [[NSAttributedString.Key : Any]?] ) -> NSAttributedString {
        

        let message = String.init(format: NSLocalizedString(self, comment: ""), arguments: replacements)
        
        let attributedString =  NSMutableAttributedString(string: message, attributes: attributes)
       
        
        for (i, replacement) in replacements.enumerated() {
            
            if let att = replacementAttributes[i] {
                
                let range = (attributedString.string.range(of: "\(replacement)".localized)?.nsRange(in: attributedString.string)) ?? NSRange(location: 0, length: 0)
                attributedString.addAttributes(att as [NSAttributedString.Key : Any], range: range)
            }
            
        }
        
        return attributedString
    }

}

HOW TO USE

//General attr: Applied to the entire string
let generalAttributes = [NSAttributedString.Key.font:  UIFont.getFont(.regular, size: 20)]


//Additional attrs applied to the replacement / dynamic bits. You can pass nil too
let nameAttributes = [ NSAttributedString.Key.backgroundColor: UIColor.red]
let companyAttributes = [ NSAttributedString.Key.foregroundColor: UIColor.blue]
        
myLabel.attributedText = "welcome message".localisedAttributedString("adam".localized, "space".localized, attributes: generalAttributes, replacementAttributes: [nameAttributes, companyAttributes] )

Rishi · Accepted Answer · 2017-09-26 19:09:31Z

Try the below code and update your logic accordingly.

    let localizableStr = "%@ has joined %@"
    let localisedStr = NSLocalizedString(localizableStr, comment: "")

    let components = localizableStr.components(separatedBy: "%@")

    let formatterStr = components.count > 2 ? components[1] : "has joined"

    let evaluatedStr = NSString(format: localisedStr as NSString, "Rishi ", "Stack OVerflow")

    let attributedStr = NSMutableAttributedString(string: evaluatedStr as String)
    attributedStr.addAttribute(NSForegroundColorAttributeName, value: UIColor.brown, range: NSMakeRange(0, attributedStr.length))

    let formatterStrRange = evaluatedStr.range(of: formatterStr, options: .caseInsensitive)
    attributedStr.addAttribute(NSForegroundColorAttributeName, value: UIColor.black, range: formatterStrRange)

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