UIWebView stringByEvaluatingJavaScriptFromString in background

Question

In an iOS app, I\'m running a fairly large script on a UIWebView using stringByEvaluatingJavaScriptFromString (large in terms of the length of the java

Answer 1

Well, I was doing the same thing. I had to run a synchronous ajax request which was freezing my UI. So this is how I fixed it :

__block NSString *message;
    dispatch_queue_t q = dispatch_queue_create("sign up Q", NULL);
    dispatch_async(q, ^{
        NSString *function = [[NSString alloc] initWithFormat: @"signup(\'%@\',\'%@\',\'%@\')",self.email.text,self.password.text,self.name.text];

        dispatch_async(dispatch_get_main_queue(), ^{
            NSString *result = [self.webView stringByEvaluatingJavaScriptFromString:function];
            NSLog(@"%@",result);

            if ([result isEqualToString:@"1"]) {
                message = [NSString stringWithFormat:@"Welcome %@",self.name.text];
                [self.activityIndicator stopAnimating];
                [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
            }

            else {
                message = [NSString stringWithFormat:@"%@ is a registered user",self.name.text];
                [self.activityIndicator stopAnimating];
                [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
            }

            UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Message" message:message delegate:self cancelButtonTitle:@"Okay" otherButtonTitles: nil];
            [alertView show];
        });
    });

The logic is simple. Go to a new thread, and from within that, dispatch to the main queue and then do the JS work and everything worked like a charm for me...