Plugins (Pro/Mobile-Only Feature)

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

Note: On the desktop platforms, plugins are a pro-only feature. For security reasons, plugins are not usable with webplayers.

In order to use a plugin you need to do two things:-

• Write functions in a C-based language and compile them into a library.
• Create a C# script which calls functions in the library.

The plugin 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 plugin when certain low-level rendering events happen (for example, when a graphics device is created), see the Native Plugin Interface page for details.

Here is a very simple example:

C File of a Minimal Plugin:

 float FooPluginFunction () { return 5.0F; } 

C# Script that Uses the Plugin:

using UnityEngine;
using System.Runtime.InteropServices;

class SomeScript : MonoBehaviour {

   #if UNITY_IPHONE || UNITY_XBOX360
   
   // On iOS and Xbox 360 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 plugin you have written, or “__Internal” if you are writing statically linked native code:

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

Creating a Plugin

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

For further details and examples, see the following pages:-

• Building Plugins for Desktop Platforms
• Building Plugins for iOS
• Building Plugins for Android

Further Information

• Native Plugin Interface - this is needed if you want to do rendering in your plugin.
• Mono Interop with native libraries.
• P-invoke documentation on MSDN.