title: Xcode Preprocessor Macros
body: <p>In Xcode, I can edit my preprocessor macros in the project settings. I want to create a macro that refers to an environment variable. Basically, I want to be able to refer to $SRC_ROOT in my code. What I currently have in my macros is:</p>
  
  <pre><code>SRC_ROOT=${SRC_ROOT}
  </code></pre>
  
  <p>but it isn't working.</p>