title: xcode conditional compilation
body: <p>I have following issue: I have an iPhone application which can be compiled using various color styles. So the goal is to have several build configurations with defined style, for instance <code>COLOR_STYLE_BLACK</code>. Style definition files should be placed under some subfolder in source tree, like, for example Classes/styles/black. Then, in App_Prefix.pch I'd like to #import files from respective subfolder, like following:</p>
  
  <pre><code>#ifdef `COLOR_STYLE_BLACK`
      #import "styles/black/DefaultStyle.h"
  #endif
  </code></pre>
  
  <p>But the issue is that I cannot make XCode to import files from subfolders. It seems XCode does not allows folder structures in project, or at least I cannot figure out how to do it.</p>
  
  <p>When I add folders as folder references to the project, XCode copies them to the Rersources folder, but does not add them to Compile sources build phase and reports errors on missing files.</p>
  
  <p>Thanks for any tip or advice on this.
  Matthes</p>