iOS UIWebView Javascript - insert data -receive callbacks?

Question

I have a webpage. I have a javascript file that does a whole lot of stuff. In the app I have an NSString with some crucial data that needs to be processed in the javascript file. How do I get my string value into a certain place in my html so my javascript can read it?

Also, the javascript will produce certain data when actions are performed (like pressing a button), how do I retrieve the data from the webview/javascript so it can be stored in the app?

Answer 1

You can call a javascript method and pass the value by using this

NSString *selectedValue = [webViewInstance stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@"getAndReturnRadioValue(%d)", questionCounterIntValue]];

But to trigger back from javascript you need to use a workaround method,

Implement the following webViewDelegate method

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

    NSLog(@"passed data from web view : %@",[[request URL] query]);

    if([[[request URL] query] isEqualToString:@"clickedOnLineNo"])
    {
        //Do your action here    
    }
}

You have to navigate to a fake URL from your javascript method like,

window.location = "someLink://yourApp/form_Submitted:param1:param2:param3";

on a button click or your required action.

You could take a look at my answer for this question Submit a form in UIWebView

Answer 2

- (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)script

sounds like exactly the method you need. If, for example, the input and output need to interact with the JavaScript can be done with a single method, you can pass a value into JavaScript and get the results with something like the following code:

NSString* jsCode = [NSString stringWithFormat:@"doSomething('%@')", dataToPass];
NSString* resultFromJavaScript = [webView stringByEvaluatingJavaScriptFromString:jsCode];