title: Dont understand how NSClassFromString can be used for conditional calling
body: <p>I have a testing class within my project that is there during the development phase but will be compiled out for the app store build.</p>
  
  <p>I've read in several books that NSClassFromString can be used to determine if a class exists with example code such as:</p>
  
  <pre><code>if (NSClassFromString(@"SomeClass") != nil)
  {
  [SomeClass someMethod];
  }
  else
  {
  code not using SomeClass
  }
  </code></pre>
  
  <p>However after putting this into practice in my project, I find that I'm getting a linking error for the target where I have removed the source file containing SomeClass.</p>
  
  <p>Therefore my conclusion is this mechanism for determining the presence/absence of a class is only useful if that class is within a library or source file where you are using other classes ( a detail which is missing from the books that mention this technique).
  Or am I missing something?</p>