How can I accurately detect if a link is clicked inside UILabels in Swift 4?

Question

Edit

See my answer for a full working solution:

I managed to solve this myself by using a UITextView instead of a UILabel

Answer 1

I wanted to avoid posting an answer since it's more a comment on Dan Bray's own answer (can't comment due to lack of rep). However, I still think it's worth sharing.

---

I made some small (what I think are) improvements to Dan Bray's answer for convenience:

• I found it a bit awkward to setup the textView with the ranges and stuff so I replaced that part with a textLink dict which stores the link strings and their respective targets. The implementing viewController only needs to set this to initialize the textView.
• I added the underline style to the links (keeping the font etc. from interface builder). Feel free to add your own styles here (like blue font color etc.).
• I reworked the callback's signature to make it more easy to be processed.
• Note that I also had to rename the delegate to linkDelegate since UITextViews do have a delegate already.

The TextView:

import UIKit

class LinkTextView: UITextView {
  private var callback: (() -> Void)?
  private var pressedTime: Int?
  private var startTime: TimeInterval?
  private var initialized = false
  var linkDelegate: LinkTextViewDelegate?
  var textLinks: [String : String] = Dictionary() {
    didSet {
        initialized = false
        styleTextLinks()
    }
  }

  override func awakeFromNib() {
    super.awakeFromNib()
    self.textContainerInset = UIEdgeInsets.zero
    self.textContainer.lineFragmentPadding = 0
    self.delaysContentTouches = true
    self.isEditable = false
    self.isUserInteractionEnabled = true
    self.isSelectable = false
    styleTextLinks()
  }

  private func styleTextLinks() {
    guard !initialized && !textLinks.isEmpty else {
        return
    }
    initialized = true

    let alignmentStyle = NSMutableParagraphStyle()
    alignmentStyle.alignment = self.textAlignment        

    let input = self.text ?? ""
    let attributes: [NSAttributedStringKey : Any] = [
        NSAttributedStringKey.foregroundColor : self.textColor!,
        NSAttributedStringKey.font : self.font!,
        .paragraphStyle : alignmentStyle
    ]
    let attributedString = NSMutableAttributedString(string: input, attributes: attributes)

    for textLink in textLinks {
        let range = (input as NSString).range(of: textLink.0)
        if range.lowerBound != NSNotFound {
            attributedString.addAttribute(.underlineStyle, value: NSUnderlineStyle.styleSingle.rawValue, range: range)
        }
    }

    attributedText = attributedString
  }

  override func touchesBegan(_ touches: Set, with event: UIEvent?) {
    startTime = Date().timeIntervalSinceReferenceDate
  }

  override func touchesEnded(_ touches: Set, with event: UIEvent?) {
    if let callback = callback {
        if let startTime = startTime {
            self.startTime = nil
            if (Date().timeIntervalSinceReferenceDate - startTime <= 0.2) {
                callback()
            }
        }
    }
  }

  override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
    var location = point
    location.x -= self.textContainerInset.left
    location.y -= self.textContainerInset.top
    if location.x > 0 && location.y > 0 {
        let index = self.layoutManager.characterIndex(for: location, in: self.textContainer, fractionOfDistanceBetweenInsertionPoints: nil)
        for textLink in textLinks {
            let range = ((text ?? "") as NSString).range(of: textLink.0)
            if NSLocationInRange(index, range) {
                callback = {
                    self.linkDelegate?.didTap(text: textLink.0, withLink: textLink.1, inTextView: self)
                }
                return self
            }
        }
    }
    callback = nil
    return nil
  }
}

The delegate:

import Foundation

protocol LinkTextViewDelegate {
  func didTap(text: String, withLink link: String, inTextView textView: LinkTextView)
}

The implementing viewController:

override func viewDidLoad() {
  super.viewDidLoad()
  myLinkTextView.linkDelegate = self
  myLinkTextView.textLinks = [
    "click here" : "https://wwww.google.com",
    "or here" : "#myOwnAppHook"
  ]
}

And last but not least a big thank you to Dan Bray, who's solution this is after all!