WhatsApp Swift UIActivityViewController Custom UIActivity

UIActivity WhatsApp

How to add WhatsApp to UIActivityViewController?

Drop the Whatsapp.swift file in your project.
Initialize the controller as described in ViewController.swift

ViewController.swift

//HOW TO USE THE WHATSAPP SHARE ACTION

    @IBAction func shareAction(sender: UIButton) {
        let objectsToShare = [message]
        let wsActivity = WhatsAppActivity()
        let activityVC = UIActivityViewController(activityItems: objectsToShare, applicationActivities: [wsActivity])
        activityVC.excludedActivityTypes = [UIActivityTypeAirDrop, UIActivityTypeAddToReadingList,UIActivityTypeCopyToPasteboard,UIActivityTypeSaveToCameraRoll,UIActivityTypePrint]
        
        self.presentViewController(activityVC, animated: true, completion: nil)
    }

Whatsapp.swift

//
//  Whatsapp.swift
//  Send2Phone
//
//  Created by Sohel Siddique on 3/27/15.
//  Copyright (c) 2015 Zuzis. All rights reserved.
//

import UIKit

class WhatsAppActivity : UIActivity{
    
    override init() {
        self.text = ""
        
    }
    
    var text:String?

    
    override func activityType()-> String {
        return NSStringFromClass(self.classForCoder)
    }
    
    override func activityImage()-> UIImage
    {
        return UIImage(named: "whatsapp2")!;
    }
    
    override func activityTitle() -> String
    {
        return "WhatsApp";
    }
    
    override class func activityCategory() -> UIActivityCategory{
        return UIActivityCategory.Share
    }

    func getURLFromMessage(message:String)-> NSURL
    {
        var url = "whatsapp://"
    
        if (message != "")
        {
            url = "\(url)send?text=\(message)"
        }
    
        return NSURL(string: url)!
    }
    
    override func canPerformWithActivityItems(activityItems: [AnyObject]) -> Bool {
        for activityItem in activityItems
        {
            if (activityItem.isKindOfClass(NSString))
            {
                self.text = activityItem as? String;
                var whatsAppURL:NSURL  = self.getURLFromMessage(self.text!)
                return UIApplication.sharedApplication().canOpenURL(whatsAppURL)
            }
        }
        return false;
    }
    
    override func prepareWithActivityItems(activityItems: [AnyObject]) {
        for activityItem in activityItems{
            if(activityItem.isKindOfClass(NSString)){
                var whatsAppUrl:NSURL = self.getURLFromMessage(self.text!)
                if(UIApplication.sharedApplication().canOpenURL(whatsAppUrl)){
                    UIApplication.sharedApplication().openURL(whatsAppUrl)
                }
                break;
            }
        }
    }
}

This is not how it's supposed to be done. You should only store the URL in prepareWithActivityItems and open it in performActivity.
See the docs on prepareWithActivityItems:

Subclasses should override this method and use it to store a reference to the data items in the activityItems parameter.

https://developer.apple.com/reference/uikit/uiactivity/1620668-preparewithactivityitems

its not working for swift 4