NSString in UIWebview

Send string to web view:

[webView stringByEvaluatingJavaScriptFromString:@"YOUR_JS_CODE_GOES_HERE"];

Send string from web view to Obj-C:

Declare that you implement the UIWebViewDelegate protocol (inside the .h file):

@interface MyViewController : UIViewController <UIWebViewDelegate> {    // your class members}// declarations of your properties and methods@end

In Objective-C (inside the .m file):

// right after creating the web viewwebView.delegate = self;

In Objective-C (inside the .m file) too:

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {    NSString *url = [[request URL] absoluteString];    static NSString *urlPrefix = @"myApp://";    if ([url hasPrefix:urlPrefix]) {        NSString *paramsString = [url substringFromIndex:[urlPrefix length]];        NSArray *paramsArray = [paramsString componentsSeparatedByString:@"&"];        int paramsAmount = [paramsArray count];        for (int i = 0; i < paramsAmount; i++) {            NSArray *keyValuePair = [[paramsArray objectAtIndex:i] componentsSeparatedByString:@"="];            NSString *key = [keyValuePair objectAtIndex:0];            NSString *value = nil;            if ([keyValuePair count] > 1) {                value = [keyValuePair objectAtIndex:1];            }            if (key && [key length] > 0) {                if (value && [value length] > 0) {                    if ([key isEqualToString:@"param"]) {                        // Use the index...                    }                }            }        }        return NO;    }    else {        return YES;    }}

Inside JS:

location.href = 'myApp://param=10';

When passing an NSString into a UIWebView (for use as a javascript String) you need to make sure to escape newlines as well as single/double quotes:

NSString *html = @"<div id='my-div'>Hello there</div>";html = [html stringByReplacingOccurrencesOfString:@"\'" withString:@"\\\'"];html = [html stringByReplacingOccurrencesOfString:@"\"" withString:@"\\\""];html = [html stringByReplacingOccurrencesOfString:@"\n" withString:@"\\n"];html = [html stringByReplacingOccurrencesOfString:@"\r" withString:@""];NSString *javaScript = [NSString stringWithFormat:@"injectSomeHtml('%@');", html];[_webView stringByEvaluatingJavaScriptFromString:javaScript];

The reverse process is well described by @Michael-Kessler