Swift 4.1 UITextView, Playground, UnsafeMutablePointer<ObjCBool> in a closure, finding ranges, adding attributes to attributed text

AttributedStringViewPlayground.swift

//: A UIKit based Playground for presenting A Textview with Attributed String text
//: Demonstrates the use of 'stop: UnsafeMutablePointer<ObjCBool>' parameter in the block of code by using 'stop[0]=true'
//: Show the assistant editor to see the Text view output.
// designed with Swift 4.1

import UIKit
import PlaygroundSupport

class MyViewController : UIViewController {
    override func loadView() {
        
        let view = UIView()
        view.backgroundColor = .white

        let textView = UITextView()
        textView.frame = CGRect(x: 5, y: 5, width: 365, height: 20 * 33)
        view.addSubview(textView)
        self.view = view
        
        enum TaskType
        {
        case kChangeColor
        case kBoldenFont
        }
        
        let attributedString = NSMutableAttributedString(string: "Roses are red, violets are blue, this objcbool unsafemutable pointer takes time to get use to.")
        
        for (task,searchWord,modifier) in [
            (task: TaskType.kBoldenFont, searchWord: "unsafemutable", modifier: nil ),
            (task: TaskType.kChangeColor, searchWord: "red", modifier: UIColor.red ),
            (task: TaskType.kChangeColor, searchWord: "blue", modifier: UIColor.blue ),
        ]
        {
            if let swiftRange = attributedString.string.range(of: searchWord)
            {
                let nsRange = NSRange(swiftRange, in: attributedString.string)
                switch task
                {
                case .kBoldenFont:
                    attributedString.addAttributes([NSAttributedStringKey.font: UIFont.boldSystemFont(ofSize: 14)], range: nsRange)
                case .kChangeColor:
                    if let theColor = modifier
                    {
                    attributedString.addAttributes([NSAttributedStringKey.foregroundColor: theColor], range: nsRange)
                    }

                }
            }
        }
      
        
//provided for reference
//attributedString.enumerateAttributes(in: NSMakeRange(0, attributedString.string.count),options: [])
//{ (attributeDict:  [NSAttributedStringKey: Any],
//        theRange: NSRange,
//        stop: UnsafeMutablePointer<ObjCBool>) in
        
        var idx = 0
        attributedString.enumerateAttributes(in: NSMakeRange(0, attributedString.string.count),options: [])
        { (attributeDict, theRange, stop) in
             print(theRange)
             print(attributeDict)
            
             var thisKey = ""
             if let aKey = attributeDict.keys.first
             {
                print(aKey.rawValue)
                thisKey = aKey.rawValue
             }
             print()
            
             switch idx {
             case 0:
                
                break
                
             case 1:
                if thisKey == "NSColor"
                {
                   print("Color found at \(theRange.location) to \(theRange.length)")
                }
                
             default:
                stop[0] = true
                break
             }
             idx += 1
          }

          textView.attributedText = attributedString
        }
}

// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()