A UITextView subclass that allows clients to register ranges of characters as "tappable", with keys to identify those ranges. A delegate can be assigned to receive callbacks when tappable ranges are tapped. When a user taps on a character in the text view which is in a registered range (with a registered key), the delegate's callback is called w…

RangeTappableTextView.swift

//
//  RangeTappableTextView.swift
//  Kalido
//
//  Created by Phlippie Bosman on 2016/11/23.
//  Copyright © 2016 Kalido. All rights reserved.
//

protocol RangeTappableTextViewDelegate: class {
    func rangeTappableTextView(_ rangeTappableTextView: RangeTappableTextView,
                               didTapCharacterInRange range: Range<Int>,
                               withKey key: Int)
}

class RangeTappableTextView: UITextView {
    weak open var rangeTappedDelegate: RangeTappableTextViewDelegate?
    fileprivate var tappableRanges: [Range<Int>] = []
    fileprivate var keys: [Int] = []
    
    /*
     Registers a range that will trigger the delegate if tapped.
     If a user taps a character covered by multiple ranges, the most recently-added range and key will be passed to the delegate.
    */
    open func registerTappableRange(_ range: Range<Int>, withKey key: Int) {
        tappableRanges.insert(range, at: 0)
        keys.insert(key, at: 0)
    }
    
    open func unregister(range: Range<Int>) {
        unregisterIfFound(index: tappableRanges.index(of: range))
    }
    
    open func unregister(key: Int) {
        unregisterIfFound(index: keys.index(of: key))
    }
    
    private func unregisterIfFound(index: Int?) {
        if let index = index {
            tappableRanges.remove(at: index)
            keys.remove(at: index)
        }
    }

    open func unregisterAll() {
        tappableRanges.removeAll()
        keys.removeAll()
    }
}

extension RangeTappableTextView {
    override func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        if let tapRecognizer = gestureRecognizer as? UITapGestureRecognizer {
            var location = tapRecognizer.location(in: self)
            location.x -= contentInset.left
            location.y -= contentInset.top
            
            let charIndex = layoutManager.characterIndex(
                for: location,
                in: textContainer,
                fractionOfDistanceBetweenInsertionPoints: nil)
            
            for (range, key) in zip(tappableRanges, keys) {
                if range.contains(charIndex) {
                    rangeTappedDelegate?.rangeTappableTextView(self, didTapCharacterInRange: range, withKey: key)
                    break
                }
            }
        }
        
        return super.gestureRecognizerShouldBegin(gestureRecognizer)
    }
}