How to underline a UILabel in swift?

Question

How to underline a UILabel in Swift? I searched the Objective-C ones but couldn't quite get them to work in Swift.

Solution 1

You can do this using NSAttributedString

Example:

let underlineAttribute = [NSAttributedString.Key.underlineStyle: NSUnderlineStyle.thick.rawValue]
let underlineAttributedString = NSAttributedString(string: "StringWithUnderLine", attributes: underlineAttribute)
myLabel.attributedText = underlineAttributedString

EDIT

To have the same attributes for all texts of one UILabel, I suggest you to subclass UILabel and overriding text, like that:

Swift 5

Same as Swift 4.2 but: You should prefer the Swift initializer NSRange over the old NSMakeRange, you can shorten to .underlineStyle and linebreaks improve readibility for long method calls.

class UnderlinedLabel: UILabel {

override var text: String? {
    didSet {
        guard let text = text else { return }
        let textRange = NSRange(location: 0, length: text.count)
        let attributedText = NSMutableAttributedString(string: text)
        attributedText.addAttribute(.underlineStyle,
                                    value: NSUnderlineStyle.single.rawValue,
                                    range: textRange)
        // Add other attributes if needed
        self.attributedText = attributedText
        }
    }
}

Swift 4.2

class UnderlinedLabel: UILabel {

override var text: String? {
    didSet {
        guard let text = text else { return }
        let textRange = NSMakeRange(0, text.count)
        let attributedText = NSMutableAttributedString(string: text)
        attributedText.addAttribute(NSAttributedString.Key.underlineStyle , value: NSUnderlineStyle.single.rawValue, range: textRange)
        // Add other attributes if needed
        self.attributedText = attributedText
        }
    }
}

Swift 3.0

class UnderlinedLabel: UILabel {
    
    override var text: String? {
        didSet {
            guard let text = text else { return }
            let textRange = NSMakeRange(0, text.characters.count)
            let attributedText = NSMutableAttributedString(string: text)
            attributedText.addAttribute(NSUnderlineStyleAttributeName , value: NSUnderlineStyle.styleSingle.rawValue, range: textRange)
            // Add other attributes if needed
            self.attributedText = attributedText
        }
    }
}

And you put your text like this :

@IBOutlet weak var label: UnderlinedLabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        label.text = "StringWithUnderLine"
    }

OLD:

Swift (2.0 to 2.3):

class UnderlinedLabel: UILabel {
    
    override var text: String? {
        didSet {
            guard let text = text else { return }
            let textRange = NSMakeRange(0, text.characters.count)
            let attributedText = NSMutableAttributedString(string: text)
            attributedText.addAttribute(NSUnderlineStyleAttributeName, value:NSUnderlineStyle.StyleSingle.rawValue, range: textRange)
            // Add other attributes if needed
            
            self.attributedText = attributedText
        }
    }
}

Swift 1.2:

class UnderlinedLabel: UILabel {
    
    override var text: String! {
        didSet {
            let textRange = NSMakeRange(0, count(text))
            let attributedText = NSMutableAttributedString(string: text)
            attributedText.addAttribute(NSUnderlineStyleAttributeName, value:NSUnderlineStyle.StyleSingle.rawValue, range: textRange)
            // Add other attributes if needed
            
            self.attributedText = attributedText
        }
    }
}

Solution 2

Swift 5 & 4.2 one liner:

label.attributedText = NSAttributedString(string: "Text", attributes:
    [.underlineStyle: NSUnderlineStyle.single.rawValue])

Swift 4 one liner:

label.attributedText = NSAttributedString(string: "Text", attributes:
    [.underlineStyle: NSUnderlineStyle.styleSingle.rawValue])

Swift 3 one liner:

label.attributedText = NSAttributedString(string: "Text", attributes:
      [NSUnderlineStyleAttributeName: NSUnderlineStyle.styleSingle.rawValue])

Solution 3

If you are looking for a way to do this without inheritance:

Swift 5

extension UILabel {
    func underline() {
        if let textString = self.text {
          let attributedString = NSMutableAttributedString(string: textString)
            attributedString.addAttribute(NSAttributedString.Key.underlineStyle,
                                          value: NSUnderlineStyle.single.rawValue,
                                          range: NSRange(location: 0, length: attributedString.length))
          attributedText = attributedString
        }
    }
}

Swift 3/4

// in swift 4 - switch NSUnderlineStyleAttributeName with NSAttributedStringKey.underlineStyle
extension UILabel {
    func underline() {
        if let textString = self.text {
          let attributedString = NSMutableAttributedString(string: textString)
          attributedString.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.styleSingle.rawValue, range: NSRange(location: 0, length: attributedString.length))
          attributedText = attributedString
        }
    }
}


extension UIButton {
  func underline() {
    let attributedString = NSMutableAttributedString(string: (self.titleLabel?.text!)!)
    attributedString.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.styleSingle.rawValue, range: NSRange(location: 0, length: (self.titleLabel?.text!.characters.count)!))
    self.setAttributedTitle(attributedString, for: .normal)
  }
}

Solution 4

Swift 5:

1- Create a String extension to get attributedText

extension String {

    var underLined: NSAttributedString {
        NSMutableAttributedString(string: self, attributes: [.underlineStyle: NSUnderlineStyle.single.rawValue])
    }

}

2- Use it

On buttons:

<#YourButton#>.setAttributedTitle(<#YourButtonTitle#>.underLined, for: .normal)

On Labels:

<#YourLabel#>.attributedText = <#YourLabelTitle#>.underLined

Or Stoyboard version

Solution 5

Just a little fix for the Shlome answer in Swift 4 and Xcode 9.

extension UILabel {
    func underline() {
        if let textString = self.text {
            let attributedString = NSMutableAttributedString(string: textString)
            attributedString.addAttribute(NSAttributedStringKey.underlineStyle,
                                          value: NSUnderlineStyle.styleSingle.rawValue,
                                          range: NSRange(location: 0, length: attributedString.length - 1))
            attributedText = attributedString
        }
    }
}

    extension UIButton {
        func underline() {
            let attributedString = NSMutableAttributedString(string: (self.titleLabel?.text!)!)
            attributedString.addAttribute(NSAttributedStringKey.underlineStyle,
                                          value: NSUnderlineStyle.styleSingle.rawValue,
                                          range: NSRange(location: 0, length: (self.titleLabel?.text!.count)!))
            self.setAttributedTitle(attributedString, for: .normal)
        }
    }

View more solutions

Comments

[Eric H]

This method fails if you rebind the text to the label.

[meaning-matters]

@EricH What do you mean?

[Skaal]

NSUnderlineStyle.styleSingle.rawValue has been renamed to NSUnderlineStyle.single.rawValue in swift 4.2

[N. Der]

How do I de-underline?

[N. Der]

What would be the best way to de-underline?

[byJeevan]

@N.Der Set again a normal text to label

[Bruno Muniz]

I've been wondering for a long time: why do we have to use rawValue otherwise it crashes?

[karthikeyan]

How you will track the touch?

[Jan Bergström]

simply beutiful and easy

[Leo Dabus]

You should pass UTF16 count instead of the character count when creating your textRange NSRange

[Leo Dabus]

You should pass UTF16 count instead of the character count when creating your NSRange

[Leo Dabus]

You should pass UTF16 count instead of the character count when creating your NSRange

[Leo Dabus]

You should pass UTF16 count instead of the character count when creating your NSRange

[boherna]

If you already have the extension for the UILabel, IMO it is simpler to call myButton.titleLabel?.underline(), or at least use it inside the underline() function in the extension for UIButton.

[João Serra]

I've changed this solution to add a underlline on initialize, this way we can use it easily with storyboards required init?(coder: NSCoder) { super.init(coder: coder) self.addUnderline() // your code }

[Ucdemir]

Better solution algorithm with better solution you can look my answer stackoverflow.com/questions/28053334/…