title: On iOS where is the NSURLCache cache stored if diskPath:nil?
body: <p>I've come across code that looks like this:</p>
  
  <pre><code>NSURLCache *URLCache = 
      [[NSURLCache alloc] initWithMemoryCapacity:1024 * 1024 
                                    diskCapacity:1024 * 1024 * 5 
                                        diskPath:nil];
  </code></pre>
  
  <p>The problem is that I haven't been able to find what's the expected behavior when diskPath is passed nil.  <a href="https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSURLCache_Class/Reference/Reference.html#//apple_ref/doc/uid/20001699-BAJJHGEA">NSURLCache docs</a> don't explicitly describe this situation nor I have been able to figure it out with my own testing.</p>
  
  <p>Where is the cache stored? or is that code above a bug?</p>
  
  <p>Thanks.</p>