Writing a class to interact with an iOS plugin in Unity.

Written by Michael on March 22, 2015

Now that I have built an iOS plugin for sharing I need to implement a wrapper class for it in C# for Unity. This post will go through the wrapper class code that I put together to add the feature of sharing to Facebook or Twitter for a Unity game for iPhone. I will go into detail about how to make the Objective-C methods available to the C# wrapper class.

From the previous post I have the following files inside the Plugins/iOS/FrispSocial folder:

  • FrispSocial.h
  • FrispSocial.mm

Here we define the class Extensions/FrispSocial/FrispAppleSocial.cs:

using UnityEngine;
using System;
using System.Collections;

using System.Runtime.InteropServices;

public class FrispAppleSocial : MonoBehaviour  {
  [DllImport ("__Internal")]
  private static extern void _Share (string text, string image);

  private static readonly FrispAppleSocial _singleton = new FrispAppleSocial ();

  private FrispAppleSocial() {}

  public static FrispAppleSocial Instance() {
    return _singleton;

  public void ShareImage(String text, Texture2D image) {
    var imageInBytes = image.EncodeToPNG();
    var base64Image = System.Convert.ToBase64String (imageInBytes);
    _Share(text, base64Image);

The Objective-C classes defined under the Plugins/iOS directory are statically linked into the executable created for the iPhone. This means that the _Share method defined in the Objective-C class exists in the executable. To get access to it we need to do an internal DLL Import of the method. The following code achieves this:

[DllImport ("__Internal")]
private static extern void _Share (string text, string image);

Given I have imported the method I can now invoke it inside the ShareImage method with the appropriate parameters.

I found the process of working with iOS and Unity quite enjoyable and not as painful as working with Android. This might be because i’m working on an iMac and I have an iPhone device. In my next post I will go over the class I wrote for unifying the Android and iOS logic.

All of the code including the Objective-C classes has been open sourced on our company github account.

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