shouldStartLoadWithRequest is not called when using AJAX/XMLHttpRequest

Question

Hi, I am trying to send method invocations from JavaScript to Objective-C and vice versa. Everything works fine for window.location triggered urls, which are catched by shouldStartLoadWithRequest. Now if I try to use an AJAX call instead, shouldStartLoadWithRequest is not called. Is there a way to do this? Mainly I do not want to be restricted to the max URL size on data that can be passed from JavaScript to Objective-C.

My UIWebViewDelegate implements:

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
 NSString *url = [[request URL] absoluteString];
 NSRange urlrange = [url rangeOfString:@"myScheme://"];
 if(urlrange.length > 0){
  NSLog(@"this is an objective-c call, do not load link: %@", [url substringWithRange:NSMakeRange(urlrange.location, [url length])] );
  return NO;
 } else {
  NSLog(@"not an objective-c call, load link: ", url );
  return YES;
 }
}

My JavaScript calls:

// works
window.location.href = "myScheme://readyHref";  

// fails
var xmlHttpReq = false;
if (window.XMLHttpRequest) {
 xmlHttpReq = new XMLHttpRequest();
} else if (window.ActiveXObject) {
 xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlHttpReq.open('GET', "myScheme://readyAJAX", false);
xmlHttpReq.send();

Answer 1

Although I could not find the answer why AJAX requests are not intercepted by shouldStartLoadWithRequest I found two workarounds. I assume that JavaScript Requests are not being intercepted but only HTML-associated / -originated requests are. If any one could verify or correct this, I'd be happy.

The two workarounds are simple. On the one hand it seems that the restriction of 256 characters in the URL does not affect MobileSafari or at least the url in that state. I read that Safari allows 80'000 charcters. However I did not feel well with that. So the workaround #2 is to use a html form that uses the POST method and set the action to your scheme. The data can be stored in the form as the value of an input field or the like. After submitting the form with JavaScript shouldStartLoadWithRequest is triggered and the data can be retrieved from HTTPBody.