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iOS UIWebView, how to block a certain URL pattern from loading?

I have an iOS app with a web view controller, which is a delegate of a web view. I would like my UIWebView to never show a url which has a certain keyword or part of a URL. (In my case, I want to block a misleading error page from the app server, which can appear in response to any request).
I'm listening to these events:
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {}
-(void)webViewDidFinishLoad:(UIWebView *)webView{}
- (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {}
I'm not sure if listening to these events is enough to make sure that all internal page redirects, including those of javascript would be inspected and the offending url will be prevented from loading.
How can I create a UIWebView which will never show a certain page?

You can check if the keyword is in the URL that was requested and stop the page from loading by returning false. I am assuming the keyword you are looking for will be in the URL? Let's pretend it's errorPage.
-(BOOL) webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
NSURL *requestedURL = request.URL
NSString *stringCheck = requestedURL.absoluteString;
// This is the important part--check if errorPage is in the URL.
NSRange range = [urlString rangeOfString:#"errorPage"];
if (range.location == NSNotFound)
return YES;
else
return NO;
}

EasyJSWebView breaks when reloading the webview

I have been implementing EasyJSWebView into a project that pops up a web view on the receipt of a push message. This works fine for the most part, until you want to reload the current webview. At that point the functionality of EasyJSWebView breaks and the javascript in the webpage cannot communicate with the objective C running in the app.
This is the code I'm using to add the interface to the webview and then load the page on the view.
_webView.delegate = self;
javaScriptInterface* interface = [javaScriptInterface new];
[self.webView addJavascriptInterfaces:interface WithName:#"interface"];
interface.webView = self;
[interface release];
[[NSURLCache sharedURLCache] removeAllCachedResponses];
[_webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:#"mywebpage.com"]]];
If I call another loadrequest on the webview, even if it is to the same page, this stops working. I have tried adding another interface object to the webview before a reload but that doesn't seem to do anything either.
At the moment I am destroying the current webview and creating a new one each time I need to do a reload or another push message is received.
Is there any fix or workaround to this? I would like to be able to use one webview for everything and not worry if it gets reloaded or not.

There's a bug in the original EasyJSWebView repository.
Just use the fork from here: https://github.com/andiradulescu/EasyJSWebView

I'm not sure if this is the best way to solute the issue, but it works in my project. My method is to create an new UIWebView before every reload or redirect request. Below is the details:
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
//'isNotFirstLoad' marks if it is the fisrt load.
if (isNotFirstLoad) {
//create an new webview
CGRect frame = _myWebView.frame;
[_myWebView removeFromSuperview];
_myWebView = [[EasyJSWebView alloc] initWithFrame:frame];
[self.view addSubview:_myWebView];
//init the new webview
_webView.delegate = self;
javaScriptInterface* interface = [javaScriptInterface new];
[self.webView addJavascriptInterfaces:interface WithName:#"interface"];
[_myWebView loadRequest:request];
//reset the firstload flag to load the new request
isNotFirstLoad = NO;
return NO;
}
isNotFirstLoad = YES;
return YES;
}

Download files on a website with Javascript using iOS

I'm trying to download a file programmly on this site, and I found that when you click the highlighted download button("下载"), it runs a Javascript: document.getElementById('downLoad').action='/download.php?fileid=11024011';downishare('0');
On my Mac, it runs fine and downloads the file when I run it on Safari. But when I use
[webView stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:#"document.getElementById('downLoad').action='/download.php?fileid=11024011'"]];
It doesn't return anything.
Does anyone know why and how can I get the download URL?
Thanks.

Well... the download url is this: http://ishare.iask.sina.com.cn/download.php?fileid=11024011
You can check it also with the 'Network' tab in chrome or firebug in firefox. BUT... when you try to access it directly, it redirects you. There might be some server side validation of the request, like the referrer url or something.

Have you tried implementing the webView delegate method shouldStartLoadWithRequest to parse through links?
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
if ([[[request URL] absoluteString] hasPrefix:#"http://ishare.iask.sina.com.cn/download.php?fileid="])
//I believe this would download everything that has a link prefix of "http://ishare.iask.sina.com.cn/download.php?fileid="
//So you should create some sort of checker to make sure it only downloads the file they select
// Determile cache file path
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *filePath = [NSString stringWithFormat:#"%#/%#", [paths objectAtIndex:0],#"index.html"];
// Download and write to file
NSURL *url = [NSURL URLWithString:[[request URL] absoluteString]];
NSData *urlData = [NSData dataWithContentsOfURL:url];
[urlData writeToFile:filePath atomically:YES];
// Load file in UIWebView
[webView loadRequest:[NSURLRequest requestWithURL:[NSURL fileURLWithPath:filePath]]];
return NO;
}
else {
return YES;
}

get javascript data from web page in mountain lion

I am extrating from a web page dynamic values generated by javascript and it worked fine on OS X Lion but failed on Mountain Lion 10.8.1 (I get empty string).
Here is the code in my controller :
-(void) addValue:(id) sender {
NSString *value = [webView stringByEvaluatingJavaScriptFromString: #"document.getElementById('xxx').textContent"];
}
- (void)webView:(WebView *)sender didFinishLoadForFrame:(WebFrame *)frame {
[self addValue:self];
}
- (void) getjavascriptValue {
[[webView mainFrame] loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:#"htmlPagePath"] ]]];
}
webView is declared as IBOutlet WebView *webView; and I made the connections of webView and frameLoadDelegate to my controller with Interface Builder.
Your help will be very much appreciated

Can I handle alert inside UIWebViewDelegate?

<script language="javascript">
alert("Hell! UIWebView!");
</script>
I can see the alert message inside my UIWebView but can I handle this situation?
Update:
I'm loading a web-page into my UIWebView:
- (void)login {
NSString *requestText = [[NSString alloc] initWithFormat: #"%#?user=%#&password=%#", DEFAULT_URL, user.name, user.password]; // YES, I'm using GET request to send password :)
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:requestText]];
[webView loadRequest:request];
}
The target page contain a JS. If user name or password is incorrect this JS show alert.
I have not any access to its sources.
I want to handle it inside my UIWebViewDelegate.

A better solution to this problem is to create a Category for UIWebView for the method
webView:runJavaScriptAlertPanelWithMessage:initiatedByFrame:
So that you can handle the alert event in any way that you'd like. I did this because I don't like the default behavior of UIWebView when it puts the filename of the source in the UIAlertView title. The Category looks something like this,
#interface UIWebView (JavaScriptAlert)
- (void)webView:(UIWebView *)sender runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WebFrame *)frame;
#end
#implementation UIWebView (JavaScriptAlert)
- (void)webView:(UIWebView *)sender runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WebFrame *)frame {
UIAlertView* dialogue = [[UIAlertView alloc] initWithTitle:nil message:message delegate:nil cancelButtonTitle:#"Okay" otherButtonTitles:nil];
[dialogue show];
[dialogue autorelease];
}
#end

This seems to do it:
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
JSContext *ctx = [webView valueForKeyPath:#"documentView.webView.mainFrame.javaScriptContext"];
ctx[#"window"][#"alert"] = ^(JSValue *message) {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"JavaScript Alert" message:[message toString] delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alert show];
};
}
Note: only tested on iOS 8.

If by "contain a flash" you mean the page you're loading into your web view has an Adobe Flash movie in it, you're out of luck, I'm afraid. Mobile Safari doesn't support Flash, and most likely never will.
In the general case, if you want JavaScript running in a web view to communicate with the native app hosting it, you can load fake URLs (for example: "myapp://alert?The+text+of+the+alert+goes+here."). That will trigger the webView:shouldStartLoadWithRequest:navigationType: delegate method. In that method, inspect the request, and if the URL being loaded is one of these internal communications, trigger the appropriate action in your app, and return NO.