Link to resources inside WebView – iPhone

Apparently there’s a bit of a gotcha according to the iPhone SDK Release Notes for iPhone OS 3.0:

Issue: UIWebView can’t load local resources in apps built against 3.0.

When using [UIWebView
loadHTMLString:baseURL:], the HTML
string should not refer to local
resources with the file:// scheme.
Instead, pass in NULL or a file://
URL for baseURL:, or include the
resources directly in the HTML with
<style> and <script> tags.

Fair enough. But passing in a standard-issue file:// URL for baseURL doesn’t quite work. However … it turns out that, if you change / to // and spaces to %20, you will be set! (Using %20 makes a lot of sense, but the double-slash part caught me by surprise.)

Let’s say you already have NSString *markup set up. Here’s all you do. (I’ve wrapped the code here for readability. You may wish to refactor/adjust to taste.)

 NSString *resourcePath = [[[[NSBundle mainBundle] resourcePath]
     stringByReplacingOccurrencesOfString:@"https://stackoverflow.com/" withString:@"//"]
     stringByReplacingOccurrencesOfString:@" " withString:@"%20"];
 [webView loadHTMLString:markup baseURL:[NSURL URLWithString:
     [NSString stringWithFormat:@"file:/%@//", resourcePath]]];

So long as your CSS, JavaScript and images are referred to by filename alone, this should do the trick in iPhone OS 3.0 where loadHTMLString:baseURL: is concerned!