title: How to import an [objective-c++] class which imports a [c++] class into an [objective-c] class?
body: <p>I have 3 files.</p>
  
  <pre><code>// A.h/A.m, Objective-C.
  #import "B.h"
  @interface A
  {
    B* b;
  }
  @end
  // Uses instance method of B in implementation.
  
  
  
  // B.h/B.mm, Objective-C++.
  #import "C.h"
  @interface B
  {
    C c;  // c is declared without pointer.
  }
  @end
  // Uses member methods of C in implementation.
  
  
  
  // C.h/C.cpp, C++.
  #include &lt;Box2D/Box2D.h&gt;  // C++ library.    
  class   C
  {
      private:
      b2World     world;
      b2Body*     ground;
      b2Body*     ball;
  
      public:
  
      PhysicsSimulator();
      ~PhysicsSimulator();
  
      void    setupWorld();
      void    cleanupWorld();
  
      void    tickWorld();
  };
  // One file of Box2D library include &lt;cassert&gt;
  </code></pre>
  
  <p>This makes compile-time error. </p>
  
  <pre><code>/Users/eonil/Work/Trials/Box2DTest/Library/Box2D/Common/b2Settings.h:22:10: fatal error: 'cassert' file not found [1]
  </code></pre>
  
  <p>It looks I have to do something special when importing Objective-C++ from Objective-C. But I can't figure out what it is. And I'm not sure even that is possible or not. What's that..?</p>