How to call Objective-C from Javascript?

Question

I have a WebView, and I want to call a view in Objective-C from JavaScript. Does someone know how I can do this?

---

I have this code in my ViewController:

- (BOOL)webView:(UIWebView *)webView2 
 shouldStartLoadWithRequest:(NSURLRequest *)request 
 navigationType:(UIWebViewNavigationType)navigationType {

 NSString *requestString = [[request URL] absoluteString];
 NSArray *components = [requestString componentsSeparatedByString:@":"];

 if ([components count] > 1 && 
  [(NSString *)[components objectAtIndex:0] isEqualToString:@"myapp"]) {
  if([(NSString *)[components objectAtIndex:1] isEqualToString:@"myfunction"]) 
  {

   NSLog([components objectAtIndex:2]); [[Airship shared] displayStoreFront]; //<- This is the code to open the Store
   NSLog([components objectAtIndex:3]); // param2
   // Call your method in Objective-C method using the above...
  }
  return NO;
 }

 return YES; // Return YES to make sure regular navigation works as expected.
}

And in Javascript:

function store(event)
{
    document.location = "myapp:" + "myfunction:" + param1 + ":" + param2;
}

But nothing happens.

Answer 1

The standard workaround for UIWebView is to set a UIWebViewDelegate, and implement the method webView:shouldStartLoadWithRequest:navigationType:. In your JavaScript code, navigate to some fake URL that encodes the information you want to pass to your app, like, say:

window.location = "fake://myApp/something_happened:param1:param2:param3";

In your delegate method, look for these fake URLs, extract the information you need, take whatever action is appropriate, and return NO to cancel the navigation. It's probably best if you defer any lengthy processing using some flavor of performSelector.