Line break after 20 characters in a label

Question

I have a label. If the text count in that label is 30, then after the 20th character there should be a line break. How can we achieve that?

I have the label setup as below.

        let label = MyLabelText()
        label.numberOfLines = 2
        label.lineBreakMode = .byTruncatingTail
        label.setContentHuggingPriority(.defaultHigh, for: .horizontal)

Both line break and number of lines are defined. But I'm not sure how to go to the second line after the 20th character.

You have to find the 20th character in the string and insert a line-break character `\n` after it and the label will render it for you. https://stackoverflow.com/q/24092884/9086770 — trndjc, Sep 23 '22 at 18:12
You could even subclass this label and implement this logic internally for a clean abstraction. — trndjc, Sep 23 '22 at 18:15

Ars_Codicis · Answer 1 · 2022-09-23T22:12:47.537

You can use a String extension:

extension String {

    mutating func insert(sourceString: String, string: String, indx: Int) {

        do {

            if indx > sourceString.count {
              
            } else {

                try insert(contentsOf: string, at: index(startIndex, offsetBy: indx))
            }

        // This do-catch is to make sure nothing happens if is an issue

        } catch Your.Execption {
          
        }
    }
}

And then use it like this:

myString.insert(sourceString: myString, string: "\n", indx: 20)

score 0 · Answer 2 · answered Sep 27 '22 at 12:47

A clean way to achieve this is to extend String so it can provide a 'wrapped' version of itself, and then use this in a subclass of UILabel to keep things clean at the point of use.

So extend String to wrap itself into a multi-line string at a certain character width:

extension String {
    func wrap(at width: Int) -> String {
        return self
            .indices
            .enumerated()
            .reduce(""){
                let charAsString = String(self[$1.1])
                let position = $1.0
                guard position != 0 else {return charAsString}
                if position.isMultiple(of: width) {
                    return $0 + "\n" + charAsString
                } else {
                    return $0 + charAsString
                }
            }
    }
}

A couple of things of note:

you need to use the original indices, not the just the length of the produced string or it's indices as adding the line break affects the number of characters
you actually want to wrap the original string, i.e. insert the line break, every width + 1 characters. Helpfully sequence enumerations are 0-indexed so you get the +1 for free :)
you could put the whole reduce closure into a single line ternary operation. I did initially and it was hideous to read, so an if...else is far more maintainable.

Once this is in place, creating the custom UILAbel is pretty straightforward. Create a subclass and override the text property:

class WrappedLabel: UILabel {
    let width: Int
    init(withWidth width: Int, frame: CGRect = .zero) {
        self.width = width
        super.init(frame: frame)
        numberOfLines = 0  //to allow auto-sizing of the label
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override var text: String? {
        set {
            guard let newValue = newValue else {return}
            super.text = newValue.wrap(at: width)
        }
        get {
            super.text
        }
    }
}

Implementation is then as simple as

let label = WrappedLabel(withWidth: 20)

Line break after 20 characters in a label

2 Answers2