Native plug-ins

Unity has extensive support for native plug-ins, which are libraries of native code written in C, C++, Objective-C, etc. Plug-ins allow your game code (written in Javascript or C#) to call functions from these libraries. This feature allows Unity to integrate with middleware libraries or existing C/C++ game code.

In order to use a native plug-in you firstly need to write functions in a C-based language to access whatever features you need and compile them into a library. In Unity, you will also need to create a C# script which calls functions in the native library.

The native plug-in should provide a simple C interface which the C# script then exposes to other user scripts. It is also possible for Unity to call functions exported by the native plug-in when certain low-level rendering events happen (for example, when a graphics device is created), see the Native plug-in interface page for details.

Example

A very simple native library with a single function might have source code that looks like this:

    float FooPluginFunction () { return 5.0F; } 

To access this code from within Unity, you could use code like the following:

    using UnityEngine;
    using System.Runtime.InteropServices;

    class SomeScript : MonoBehaviour {

       #if UNITY_IPHONE
   
       // On iOS plugins are statically linked into
       // the executable, so we have to use __Internal as the
       // library name.
       [DllImport ("__Internal")]

       #else

       // Other platforms load plugins dynamically, so pass the name
       // of the plugin's dynamic library.
       [DllImport ("PluginName")]
    
       #endif

       private static extern float FooPluginFunction ();

       void Awake () {
          // Calls the FooPluginFunction inside the plugin
          // And prints 5 to the console
          print (FooPluginFunction ());
       }
    }

Note that when using Javascript you will need to use the following syntax, where DLLName is the name of the plug-in you have written, or “__Internal” if you are writing statically linked native code:

    @DllImport (DLLName)
    static private function FooPluginFunction () : float {};

Creating a native plug-in

In general, plug-ins are built with native code compilers on the target platform. Since plug-in functions use a C-based call interface, you must avoid name mangling issues when using C++ or Objective-C.

Further Information

• Native plug-in interface (this is needed if you want to do rendering in your plug-in)
• Mono Interop with native libraries
• P-invoke documentation on MSDN