Communication between iOS's native app and webpage's javascript

Question

I have a webpage loaded in a UIWebView, and a javascript function of the page needs to data from native iOs app, a NSString. How can a Js function access the data in native app

Answer 1

[webView loadHTMLString:@"" 
      baseURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] resourcePath]]];

NSString *result = [webView stringByEvaluatingJavaScriptFromString:@"function(parameter)"];

Give feedback to iOS

window.location = customprefix://function/parameter=value

- (BOOL)webView:(UIWebView*)webView shouldStartLoadWithRequest:(NSURLRequest*)request navigationType:(UIWebViewNavigationType)navigationType {
    if ([[URL scheme] isEqualToString:@"customprefix"]) {
        // handle function name and paramters
    }
}

I also wrote a guide on how to call and handle different javascript functions from within iOS. http://www.dplusmpage.com/2012/07/20/execute-javascript-on-ios/