title: implicit conversion of objective-c pointer type nsstring to cpointer type 'CFTypeRef'
body: <p>I am using <a href="https://stackoverflow.com/questions/3334047/how-to-add-a-contact-from-my-app-to-iphone-address-book">this link</a> for storing contact info, in my opinion there is little bit problem with ARC.</p>
  
  <p>when I use this below code it's work fine.</p>
  
  <pre><code>ABAddressBookRef libroDirec = ABAddressBookCreate();
  
  ABRecordRef persona = ABPersonCreate();
  
  ABRecordSetValue(persona, kABPersonFirstNameProperty, @"JustTESTING", nil);
  </code></pre>
  
  <p>on other hand when i use this below code its gives error  <strong>implicit conversion of objective-c pointer type nsstring to cpointer type 'CFTypeRef'</strong></p>
  
  <pre><code>NSString * prefName = ref.fName; 
  
  ABAddressBookRef libroDirec = ABAddressBookCreate();
  
  ABRecordRef persona = ABPersonCreate();
  
  ABRecordSetValue(persona, kABPersonFirstNameProperty, prefName, nil);// error in prefName
  </code></pre>
  
  <p>Thanks</p>