title: How to use static C++ library in unity?
body: <p>I'm building an app on iOS based on Unity3d, and I need a static library(.a) linked in unity. 
  But it seems you can't import .a libraries directly in Unity, and you have to import it in XCode projects. You have to wrote some extra code in XCode as middleware. Since communicate between C# &amp; C++ will cause some performance issue (about 3-5 frames delay), is there the only way to use static C++ library in Unity?</p>