Swift: using evaluateJavascript

Question

I'm fairly new to Swift development, and I have a hybrid app I am developing that I have wired up authentication to. When a user authenticates with the fingerprint sensor on a device, I want to trigger a JS or otherwise interact with the WKWebView... but for some reason, I can't seem to get it to work. I can do simple things like change the window HREF... but if I do something more complex, it either does nothing, or fails.

Here is the code of my viewController:

    import UIKit
    import WebKit
    import LocalAuthentication

    class ViewController: UIViewController, WKScriptMessageHandler, WKUIDelegate, WKNavigationDelegate {

        @IBOutlet var containerView : UIView! = nil

        // @IBOutlet weak var webView: UIWebView!
        var webView: WKWebView?
        var contentController = WKUserContentController();

        @IBOutlet var activityIndicatorView: UIActivityIndicatorView!

        override func viewDidLoad() {
            super.viewDidLoad()

            // append the userAgent and ensure it contains our browser detect regEx
            let userAgent = UIWebView().stringByEvaluatingJavaScriptFromString("navigator.userAgent")! + " iPad"
            NSUserDefaults.standardUserDefaults().registerDefaults(["UserAgent" : userAgent])

            // add JS content controller

            var config = WKWebViewConfiguration()
            config.userContentController = contentController

            // instantiate the web view
            let webView = WKWebView(frame: CGRectZero, configuration: config)
            webView.setTranslatesAutoresizingMaskIntoConstraints(false)
            webView.navigationDelegate = self
            view.addSubview(webView)

            // customize sizing
            view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|[webView]|", options: NSLayoutFormatOptions.allZeros, metrics: nil, views: ["webView": webView]))

            view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[webView]|", options: NSLayoutFormatOptions.allZeros, metrics: nil, views: ["webView": webView]))

            // open the URL for the app
            let urlPath = "http://im_a_url"
            let url: NSURL = NSURL(string: urlPath)!
            let request = NSURLRequest(URL: url)
            webView.loadRequest(request)

        }

        override func didReceiveMemoryWarning() {
            super.didReceiveMemoryWarning()
            // Dispose of any resources that can be recreated.
        }

        func webView(webView: WKWebView!, didStartProvisionalNavigation navigation: WKNavigation!) {
          UIApplication.sharedApplication().networkActivityIndicatorVisible = true
        }

        func webView(webView: WKWebView!, didFinishNavigation navigation: WKNavigation!) {
   UIApplication.sharedApplication().networkActivityIndicatorVisible = false

            // trigger authentication
            authenticateUser()

        }

        func userContentController(userContentController: WKUserContentController, didReceiveScriptMessage message: WKScriptMessage) {

        }

        func logInWithStoredCredentials() {
            println("successful auth - log in");
            // TO DO - use core data to stor user credentials
            webView!.evaluateJavaScript("document.getElementById('anonymousFormSubmit').click();", nil)

        }

        func authenticateUser() {
            // Get the local authentication context.
            let context = LAContext()

            // Declare a NSError variable.
            var error: NSError?

            // Set the reason string that will appear on the authentication alert.
            var reasonString = "Authentication is needed to access aware360Suite."

            // Check if the device can evaluate the policy.
            if context.canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, error: &error) {
                [context .evaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, localizedReason: reasonString, reply: { (success: Bool, evalPolicyError: NSError?) -> Void in

                    if success {
                        self.logInWithStoredCredentials()
                        // self.webView?.evaluateJavaScript("document.getElementById('auiAuthSubmitBtn').click();", nil)
                    }
                    else{
                        // If authentication failed then show a message to the console with a short description.
                        // In case that the error is a user fallback, then show the password alert view.
                        println(evalPolicyError?.localizedDescription)

                        switch evalPolicyError!.code {

                        case LAError.SystemCancel.rawValue:
                            println("Authentication was cancelled by the system")

                        case LAError.UserCancel.rawValue:
                            println("Authentication was cancelled by the user")

                        case LAError.UserFallback.rawValue:
                            println("User selected to enter custom password")
                            // self.showPasswordAlert()

                        default:
                            println("Authentication failed")
                            // self.showPasswordAlert()
                        }
                    }

                })]
            }
            else{
                // If the security policy cannot be evaluated then show a short message depending on the error.
                switch error!.code{

                case LAError.TouchIDNotEnrolled.rawValue:
                    println("TouchID is not enrolled")

                case LAError.PasscodeNotSet.rawValue:
                    println("A passcode has not been set")

                default:
                    // The LAError.TouchIDNotAvailable case.
                    println("TouchID not available")
                }


            }

        }

    }

The issue is in the successful authentication method:

func logInWithStoredCredentials() {
        println("successful auth - log in");
        // TO DO - use core data to use stored user credentials
        webView!.evaluateJavaScript("document.getElementById('anonymousFormSubmit').click();", nil)

    }

I cannot seem to get a handle to the webView here. If I attempt to actually evaluate script here, it throws the following error:

2015-02-10 17:07:32.912 A360[2282:462860] -[UIWebView evaluateJavaScript:completionHandler:]: unrecognized selector sent to instance 0x1741897f0
2015-02-10 17:07:32.916 A360[2282:462860] <NSXPCConnection: 0x178103960> connection to service named com.apple.CoreAuthentication.daemon: Warning: Exception caught during decoding of received reply to message 'evaluatePolicy:options:reply:', dropping incoming message and calling failure block.

Exception: -[UIWebView evaluateJavaScript:completionHandler:]: unrecognized selector sent to instance 0x1741897f0

I'm quite at a loss. I know I don't have a proper handle to the WebView here, because I know that if I attempt an operation like this immediately after having had a successful navigation from the view, it will work fine, e.g.:

func webView(webView: WKWebView!, didFinishNavigation navigation: WKNavigation!) {
        UIApplication.sharedApplication().networkActivityIndicatorVisible = false

        webView.evaluateJavaScript("document.getElementById('anonymousFormSubmit').click();", nil)

    }

So clearly in my logInWithStoredCredentials function it has lost the context of the webView.

How can I get a proper handle to the webView in my logInWithStoredCredentials func?

Sorry all - I know this is a rather basic question, but I have been banging my head against it for hours now, and this is a very pressing issue that I must resolve quickly.

Answer 1

You have var webView: WKWebView? in your class but then redefine it in viewDidLoad as let webView = WKWebView(frame: CGRectZero, configuration: config) Remove the let in front of the webView and it should work.

Answer 2

It looks like you have UIWebView instead of WKWebView in your UI:

Exception: -[UIWebView evaluateJavaScript:completionHandler:]: unrecognized selector sent to instance 0x1741897f0

You should instantiate a WKWebView instance instead. Also note that WKWebView cannot be created in Interface Builder, you will have to add it to the view hierarchy at runtime.