UIWebview. How to call javascript functions from objective-c

I wrote about this long time ago but only to remember how simple it is.

1) Write the javascript function in your HTML file

function callMePlease () {
    // Your code here
}

2) Use this line to call the function from Objective-C using your  UIWebView object.

[webview stringByEvaluatingJavaScriptFromString:@"callMePlease()"];

For example if we only want to execute some javascript code in our webview we can use:

NSInteger pos = 100;NSString* s=[[NSString alloc] initWithFormat:@"window.scrollTo(%i, 0)",pos];[webViewMenu stringByEvaluatingJavaScriptFromString:s];

If we want to call a Objective-C function from our JavaScript code... things are a little bit more difficult:

1) In Objective C we must have

- someFunctionOnInit {

    

    webView = [[UIWebView alloc] init];

    // Register the UIWebViewDelegate in order to shouldStartLoadWithRequest to be called (next function)

    webView.delegate = self;

    

}

// This function is called on all location change :

- (BOOL)webView:(UIWebView *)webView2

shouldStartLoadWithRequest:(NSURLRequest *)request

 navigationType:(UIWebViewNavigationType)navigationType {

    

    // Intercept custom location change, URL begins with "js-call:"

    if ([[[request URL] absoluteString] hasPrefix:@"js-call:"]) {

        

        // Extract the selector name from the URL

        NSArray *components = [requestString componentsSeparatedByString:@":"];

        NSString *function = [components objectAtIndex:1];

        

        // Call the given selector

        [self performSelector:NSSelectorFromString(functionName)];

        

        // Cancel the location change

        return NO;

    }

    

    // Accept this location change

    return YES;

    

}

- (void)myObjectiveCFunction {

    

    // Do whatever you want!

    

}

There are another ways to do the same but it is enough for today. For more information check this.

Cheers