How to customize String in specific range? - Swift

Question

I'm a beginner in Swift and I want to make a custom Label on some letters the font to be bigger, and on some others to be smaller.

Like on image:

Click here to open the image

So, the currency symbol and decimal points should be in a smaller font than other numbers.

The code I tried to implement is:

// Used this function to get the index of decimal point (.) from the string.
func getDecimalIndex(text: String) -> Int {
    let myText = text.firstIndex(of: ".")
    return myText?.utf16Offset(in: text) ?? 0
}

func setupLabel(text: String) {
    guard !text.isEmpty else { return }
    
    let attributedString = NSMutableAttributedString(string: text)
    let decimalStart = getDecimalIndex(text: attributedString.string)
    attributedString.addAttribute(.font,
                                  value: UIFont.systemFont(ofSize: 22),
                                  range: NSRange(location: decimalStart, length: attributedString.length))
    
    myLabel.attributedText = attributedString
}

setupLabel(text: "$1100.33")
setupLabel(text: "1100.33€")

Whenever I load the app, it crashes on this line:

    attributedString.addAttribute(.font,
                                  value: UIFont.systemFont(ofSize: 22),
                                  range: NSRange(location: decimalStart, length: attributedString.length))

And the error in console is:

Terminating app due to uncaught exception 'NSRangeException', reason: 'NSMutableRLEArray objectAtIndex:effectiveRange:: Out of bounds'

What might be wrong?

Thank you in advance for your contribution.

Answer 1

Instead of setting NSRange for attributedString you can use several string with several attributedString-attributes.

func setupLabel(textSmall: String, textLarge : String) {
    let attributeSmall =  [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 15)]
    let attributeLarge =  [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 22)]
    
    let attr1 = NSMutableAttributedString(string: textSmall, attributes: attributeSmall)
    let attr2 = NSMutableAttributedString(string: textLarge, attributes: attributeLarge)
    
    attr2.append(attr1)
    
    myLabel.attributedText = attr2
}

use this function by splitting your string with .

let yourValue = "$1100.33"
let smallTxt = yourValue.components(separatedBy: ".")[1]
let largeTxt = "\(yourValue.components(separatedBy: ".")[0])."
setupLabel(textSmall: smallTxt, textLarge: largeTxt)