title: Associate POD Spec attributes to different Build Settings from their Xcode Configuration (e.g. Release, Debug)
body: <p>I'm trying to create a POD spec for an existing library project.</p>
  
  <p>In the Xcode project, the build settings define different Preprocessor macros for different Build Configurations (e.g.: "Debug" and "Release")</p>
  
  <p>For example:</p>
  
  <p>For the "Debug" Configuration:</p>
  
  <pre><code>GCC_PREPROCESSOR_DEFINITIONS = DEBUG=1 
  </code></pre>
  
  <p>For the "Release" Configuration:</p>
  
  <pre><code>GCC_PREPROCESSOR_DEFINITIONS = NDEBUG NS_BLOCK_ASSERTIONS
  </code></pre>
  
  <p><strong>How do I map these settings to the corresponding POD spec?</strong></p>
  
  <p>For example:</p>
  
  <pre><code>spec.compiler_flags = '-DDEBUG=1'
  </code></pre>
  
  <p>and</p>
  
  <pre><code>spec.compiler_flags = '-DNDEBUG -DNS_BLOCK_ASSERTIONS'
  </code></pre>
  
  <p>Unfortunately, the official documentation in general is mostly more confusing and unclear, than really helpful:</p>
  
  <p><a href="http://guides.cocoapods.org/syntax/podspec.html#group_build_settings">Build settings</a></p>
  
  <blockquote>
    <p><strong>Build settings</strong></p>
    
    <p>In this group are listed the attributes related to the configuration of the build environment that should be used to build the library.</p>
    
    <p>If not defined in a subspec the attributes of this group inherit the value of the parent.</p>
    
    <p>Examples:</p>
    
    <p>spec.compiler_flags = '-DOS_OBJECT_USE_OBJC=0', '-Wno-format'</p>
  </blockquote>
  
  <p>Intuitively, I would do something like this:</p>
  
  <pre><code>configuration :Debug do
      spec.compiler_flags = '-DDEBUG=1'
  end
  
  configuration :Release do
      spec.compiler_flags = '-DNDEBUG -DNS_BLOCK_ASSERTIONS'
  end
  </code></pre>
  
  <p>However, that's guessing.</p>