1. Build Integration

import Razorpay

class ViewController: UIViewController, RazorpayPaymentCompletionProtocol, WKNavigationDelegate {
// typealias Razorpay = RazorpayCheckout
    var webView: WKWebView!
    var razorpay: RazorpayCheckout!
    .
    .
    override func viewDidLoad() {
        super.viewDidLoad()
        self.webView = WKWebView(frame: self.view.frame)
        self.razorpay = RazorpayCheckout.initWithKey("Key", andDelegate: self, withPaymentWebView: self.webView)
        self.view.addSubview(self.webView)
    }
}

curl -X POST https://api.razorpay.com/v1/orders 
-U [YOUR_KEY_ID]:[YOUR_KEY_SECRET]
-H 'content-type:application/json'
-d '{
    "amount": 100,
    "currency": "MYR",
    "receipt": "qwsaq1",
    "partial_payment": true,
    "first_payment_min_amount": 230,
    "notes": {
      "key1": "value3",
      "key2": "value2"
    }
  }'

self.razorpay.getPaymentMethods(withOptions: nil, withSuccessCallback: {methods in
     paymentMethods = methods
    }){ error in
        errorDescription = error
    }

let options: [String:Any] = [
            "amount": 100, // amount in currency subunits.
            "currency": "MYR",//We support more that 92 international currencies.
            "email": "gaurav.kumar@example.com",
            "contact": "9090980808",
            "order_id": "order_DBJOWzybf0sJbb",//From response of Step 3
            "method": "card",
            "card[name]": "Gaurav Kumar",
            "card[number]": "5272008806235704",
            "card[expiry_month]": 06,
            "card[expiry_year]": 30,
            "card[cvv]": "123"
        ]
razorpay.authorize(options)

override func viewDidLoad() {
    super.viewDidLoad()
    .
    .
    self.webView.navigationDelegate = self
}

public func webView(_ webView: WKWebView, didCommit navigation: WKNavigation!){
    if razorpay != nil{
        self.razorpay.webView(webView, didCommit: navigation)
    }
}

public func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError er: Error) {
    if razorpay != nil{
        self.razorpay.webView(webView, didFailProvisionalNavigation: navigation, withError: er)
    }
}

public func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError er: Error){
    if razorpay != nil{
        self.razorpay.webView(webView, didFail: navigation, withError: er)
    }
}

public func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!){
    if razorpay != nil{
        self.razorpay.webView(webView, didFinish: navigation)
    }
}

func onPaymentError(_ code: Int32, description str: String, andData response: [AnyHashable : Any]){
    let alertController = UIAlertController(title: "FAILURE", message: str, preferredStyle: UIAlertControllerStyle.alert)
    let cancelAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.cancel, handler: nil)
    alertController.addAction(cancelAction)
    //self.view = view that controller manages
    self.view.sendSubview(toBack: self.webView)
    navBar.isHidden = true
    navBar.isUserInteractionEnabled = false
    self.view.window?.rootViewController?.present(alertController, animated: true, completion: nil)
    self.razorpay = nil
}

func onPaymentSuccess(_ payment_id: String, andData response: [AnyHashable : Any]){
    let alertController = UIAlertController(title: "SUCCESS", message: "Payment Id \(payment_id)", preferredStyle: UIAlertControllerStyle.alert)
    let cancelAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.cancel, handler: nil)
    alertController.addAction(cancelAction)
    //self.view = view that controller manages
    self.view.sendSubview(toBack: self.webView)
    navBar.isHidden = true
    navBar.isUserInteractionEnabled = false
    self.view.window?.rootViewController?.present(alertController, animated: true, completion: nil)
    self.razorpay = nil
}

//MARK: Action functions
@IBAction func cancel(_ sender: Any){

    let alertController = UIAlertController(title: "Cancel Transaction", message: "Are you sure you want to cancel the current transaction ? The page will go back to the checkout page, where you can choose another payment option", preferredStyle: UIAlertControllerStyle.alert)

    let cancelAction = UIAlertAction(title: "Do Not Cancel", style: UIAlertActionStyle.cancel, handler: nil)
    let okayAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.destructive, handler: { action in
        self.razorpay.userCancelledPayment()
        } )

    alertController.addAction(cancelAction)
    alertController.addAction(okayAction)

    self.view.window?.rootViewController?.present(alertController, animated: true, completion: nil)
}

RazorpayClient razorpay = new RazorpayClient("[YOUR_KEY_ID]", "[YOUR_KEY_SECRET]");

String secret = "EnLs21M47BllR3X8PSFtjtbd";

JSONObject options = new JSONObject();
options.put("razorpay_order_id", "order_IEIaMR65cu6nz3");
options.put("razorpay_payment_id", "pay_IH4NVgf4Dreq1l");
options.put("razorpay_signature", "0d4e745a1838664ad6c9c9902212a32d627d68e917290b0ad5f08ff4561bc50f");

boolean status =  Utils.verifyPaymentSignature(options, secret);