Unity Scripting armv7 Error

I'm attempting to write my first unity script. This is the code for a file called TestPlugin.cs that is located in Assets/Plugins:

 using UnityEngine; 
 using System.Runtime.InteropServices;

 public class TestPlugin : MonoBehaviour 
 {
     [DllImport ("__Internal")]
     private static extern int getString ();

     public static void Awake () {
       print (getString ());
     }
 } 

This is the code for two files that I import into the generated xCode project's classes folder:

TestPlugin.h:

 #import <Foundation/Foundation.h>

 @interface TestPlugin : NSObject

 -(int)getString;

 @end

TestPlugin.m:

 #import "TestPlugin.h"

 @implementation TestPlugin

 - (id)init
 {
     self = [super init];
     if (self) {
         // Initialization code here.
     }
 
     return self;
 }

 - (int)getString
 {
     return 7;
 }

 @end

Finally this is the javascript file that sits inside the Asset folder.

TestPluginTest.js:

 function Update () 
 {
 TestPlugin.Awake ();
 }

Also, please note that i'm not necessarily expecting this all to work, just to compile at this point (though extra pointers and tips are welcome)

The error I get in xCode when trying to build onto iPhone (actual device) is this:

Undefined symbols for architecture armv7: "_getString", referenced from: RegisterMonoModules() in RegisterMonoModules.o ld: symbol(s) not found for architecture armv7 collect2: ld returned 1 exit status

"_getString", referenced from:

RegisterMonoModules() in RegisterMonoModules.o

ld: symbol(s) not found for architecture armv7

collect2: ld returned 1 exit status

I'm stumped! Thanks in advance!