title: NSPropertyListSerialization propertyListWithData produces incompatible conversion warning/error
body: <p>I'm trying to read in data from a plist, using this code:</p>
  
  <pre><code>NSString *error;    
  NSData * tempData = [[NSData alloc] initWithContentsOfFile:@"Data.plist"];
  NSDictionary *temp = [NSPropertyListSerialization propertyListWithData:tempData options:NSPropertyListImmutable format:NSPropertyListXMLFormat_v1_0 error:&amp;error];
  </code></pre>
  
  <p>It kicks out a warning/error stating:</p>
  
  <blockquote>
    <p>"Incompatible integer to pointer conversion sending 'int' to parameter of type 'NSPropertyListFormat' (aka 'unsigned int *'). </p>
  </blockquote>
  
  <p>I've no idea what's going on. I chose the NSPropertyListXMLFormat_v1_0 from the code-hinting choices.</p>
  
  <p>Also, I can't find the rationale for this in the documentation so far: why do you have to declare a pointer variable for "error", and then use "&amp;error" as the argument for error:. What is the ampersand for?</p>