shouldStartLoadWithRequest: not called for images - ios

Question

I have a UIWebView and I make it load an HTML string. The string contains http urls to images. The images get loaded, but shouldStartLoadWithRequest: method is not called for them. It is called just once, for about : blank. However all the image requests are successfully passed into my NSURLCache subclass, into cachedResponseForRequest: method. But I would like to handle the requests in the shouldStartLoadWithRequest: method. Can anything be done about that? How can I make these requests go into the delegate method?
Here is the code:
#interface URLCache : NSURLCache
#end
#implementation URLCache
- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request
{
NSLog(#"REQUEST = %#", request.URL);
return [super cachedResponseForRequest:request];
}
#end
#interface ViewController ()<UIWebViewDelegate>
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
[NSURLCache setSharedURLCache:[URLCache new]];
NSString* path = [[NSBundle mainBundle] pathForResource:#"test" ofType:#"html"];
NSString* html = [NSString stringWithContentsOfFile:path
encoding:NSUTF8StringEncoding
error:nil];
self.webView.delegate = self;
[self.webView loadHTMLString:html baseURL:nil];
}
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
NSLog(#"URL = %#", request.URL);
return YES;
}
#end

Answer 1

The shouldStartLoadWithRequest method is called only for page loads (that is, when the page as a whole gets loaded or when a frame's contents get loaded), not when loading individual resources such as images, JavaScript, or CSS.
If you want to manipulate all HTTP/HTTPS requests from a UIWebView, the only way I'm aware of to do so is by using a custom NSURLProtocol subclass. See Apple's Custom HTTP Protocol sample code project for an example of how to do this.