swift nsurlprotocol

You can do that using NSURLProtocol, here's a quick example:
Subclass NSURLProtocol class Interceptor: NSURLProtocol { override class func canonicalRequestForRequest(request: NSURLRequest) -> NSURLRequest { return request } override class func canInitWithRequest(request: NSURLRequest) -> Bool { // returns true for the requests we want to intercept (*.png) return request.URL.pathExtension == "png" } override func startLoading() { // a request for a png file starts loading // custom response let response = NSURLResponse(URL: request.URL, MIMEType: "image/png", expectedContentLength: -1, textEncodingName: nil) if let client = self.client { client.URLProtocol(self, didReceiveResponse: response, cacheStoragePolicy: .NotAllowed) // reply with data from a local file client.URLProtocol(self, didLoadData: NSData(contentsOfFile: "local file path")!) client.URLProtocolDidFinishLoading(self) } } override func stopLoading() { } }
Somewhere in your code, register the Interceptor class:
NSURLProtocol.registerClass(Interceptor)
There's also a nice article on NSHipster if you want to read more about NSURLProtocol.
Thanks a lot - works like a charm! :)