UIWebView Delegate get MIME Type - objective-c

Question

The UIWebView does not automatically support processing of Passbook .pkpass files.
In this technical note, Apple recommend implementing a check via the UIWebViewDelegate methods to sniff out the MIME type and process it accordingly.
To add passes using a UIWebView, implement the appropriate
UIWebViewDelegate methods to identify when the view loads data with a
MIME type of application/vnd.apple.pkpass
However, I cannot find anything within the UIWebView Delegate Protocol Reference that is capable of providing the MIME type.
I can successfully download and process files directly using an NSURLConnection delegate with no problem, but what I wish to achieve is for passes to be properly processed if a user clicks on an Add To Passbook button while browsing within a UIWebView. Since I do not know the link, and many providers do not suffix their links with a .pkpass extension, following Apple's advice of examining the MIME type seems the best way to go.
I have tried adding the following
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)newRequest
navigationType:(UIWebViewNavigationType)navigationType
{
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:[newRequest URL]];
// Spoof iOS Safari headers for sites that sniff the User Agent
[req addValue:#"Mozilla/5.0 (iPhone; CPU iPhone OS 6_1 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A5376e Safari/8536.25" forHTTPHeaderField:#"User-Agent"];
NSURLConnection *conn = [NSURLConnection connectionWithRequest:newRequest delegate:self];
return YES;
}
My NSURLConnection delegate:
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
NSString *mime = [response MIMEType];
if ([mime isEqualToString:#"application/vnd.apple.pkpass"] && ![_data length]) {
_data = nil; // clear any old data
_data = [[NSMutableData alloc] init];
[_webPanel stopLoading];
}
}
-(void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data
{
[_data appendData:data];
NSLog(#"Size: %d", [_data length]);
}
-(void)connectionDidFinishLoading:(NSURLConnection*)connection
{
if ([_data length]) {
PKAddPassesViewController *pkvc = [PassKitAPI presentPKPassFileFromData:_data];
pkvc.delegate = self;
[self presentViewController:pkvc
animated:YES
completion:nil];
}
}
The NSURLConnection delegates work fine when a connection is invoked directly, without the UIWebView. However, when I try launching an NSURLConnection from the UIWebView delegate the pass download fails because the only 80% or so of the .pkpass is being downloaded (I get a random mismatch of bytes in the _data variable and the Content-Length header).
So, my questions:
Is there an easier way to get hold of a MIME type, directly from the UIWebView Delegate methods?
If not, then am I going about this the right way with opening up a parallel NSURLConnection, or is there a better way?
If an NSURLConnection is the way to go, then what could be causing it to stop short of downloading the full file?

Answer 1

Just use js
let contentType = webView.stringByEvaluatingJavaScript(from: "document.contentType;")

Answer 2

- (BOOL)webView:(UIWebView*)webView shouldStartLoadWithRequest:(NSURLRequest*)request navigationType:(UIWebViewNavigationType)navigationType {
NSURL *url = request.URL;
NSURLRequest *req = [NSURLRequest requestWithURL:url];
NSURLConnection *conn = [NSURLConnection connectionWithRequest:req delegate:self];
[conn start];
return YES;
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
NSString *mime = [response MIMEType];
NSLog(#"%#",mime);
}

Answer 3

You could try subclassing NSURLProtocol and handling the response information parsing there.
Look at
- (void)URLProtocol:(NSURLProtocol *)protocol didReceiveResponse:(NSURLResponse *)response cacheStoragePolicy:(NSURLCacheStoragePolicy)policy
Don't forget to about subresources also using these hooks.