title: Create constant NSString from constant CFStringRef
body: <p>I am attempting to create a Cocoa Framework that is an object-oriented wrapper around a procedural framework written in the Core Foundation. The procedural framework has a number of constants that are all defined as <code>extern CFStringRef constantName</code>.</p>
  
  <p>How should I create NSString constants that directly map to the procedural constants so that in my framework I can simply cast the NSString constant to the CFStringRef constant within the framework such that the developer using my framework does not need to be aware of the casts himself.</p>
  
  <p>Every thing that I have tried results in the compiler error <code>Initializer element is not constant</code>. This is the pattern I would like to use:</p>
  
  <p>Constants.h:</p>
  
  <pre><code>extern NSString * myConstant
  </code></pre>
  
  <p>Constants.m:</p>
  
  <pre><code>#import "Constants.h"
  NSString *myConstant = ConstantFromCFStringRef;
  </code></pre>
  
  <p>I am successfully declaring constant values with NSString in Constants.m using <code>NSString *aConstant = @"someStringLiteral"</code> but in this case, I want to have the same value as the <code>CFStringRef</code>s that I cannot ignore.</p>