Calling an Objective-C function from JavaScript hosted on some web page

Question

I have an IOS application which has a web browser in it.

When this web browser is displayed, it navigates to a page on Internet, say http://myexample.com/myiosapp.

Is it possible to place a javascript code on this web site, which, when downloaded to phone, communicates with the native application? Can it call an Objective-C method, or write something to storage space of this application?

Ex. Code hosted on myexample.com/myios app:

function saveSomeString() {
    xcode.Save("somestring");
}

should call an Objective-C function named Save, which saves incoming string parameter to local storage.

You can use local storage in js it's really simple! See diveintohtml5.info/storage.html — Alexandre Khoury
– Alexandre Khoury, Commented Nov 27, 2012 at 14:34
But after using local storage, can I read that information by XCode? — Serhat Ozgel
– Serhat Ozgel, Commented Nov 27, 2012 at 14:38
@SerhatÖzgel: XCode is a development environment, not a programming language. So it has no methods. You probably mean an Objective-C method. I've changed the title and the tags accordingly. — Codo
– Codo, Commented Nov 27, 2012 at 14:51

alemangui · Accepted Answer · 2012-11-27 14:58:04Z

6

Yes, you can, but it is a bit hacky.

On the Objective-C side:

Basically, in the UIWebView, you will use method shouldStartLoadWithRequest (from the UIWebViewDelegate) which is called before a URL request starts:

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

On Javascript side:

Your javascript code will navigate to a 'fake' URL that you will filter on the method above. Something like:

window.location = "js2objc://save:param";

Back on the Objective-C side:

Inside the method I mentioned earlier, you look for the keyword js2objc (or whichever you choose) and then extract the info and take any appropriate action:

if([[url scheme] isEqualToString:@"js2objc"]){
    // extract the parameters and save them, o do whatever action you need
    return NO;  // so the UIWebView doesn't actually follow the url
}

edited Nov 27, 2012 at 14:58

answered Nov 27, 2012 at 14:44

alemangui

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2 Comments

Serhat Ozgel Over a year ago

This should do the trick, thanks. I'll accept it once I try it.

alemangui Over a year ago

I found a tutorial that describes the above step-by-step. blog.techno-barje.fr/post/2010/10/06/…

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