Problem with script

I'm following a course over at digital tutors C# for unity and I'm having problems with the script. I'm not getting any errors at all but it is not doing what it is supposed to do. Nothing happens when I push the spacebar or I. Here is the script any help would be greatly appreciated.

 using UnityEngine;
 using System.Collections;
 
 public class Lesson_10 : MonoBehaviour 
 {
     public int weapon = 0;
     private string weaponName = null;
     private string addedItems = null;
     //public int inventorySpace = 5;//Variable that specifies number of elements in inventory list
 
 
     
     // Use this for initialization
     void Start () 
     {
         
     }
     
     // Update is called once per frame
     void Update () 
     {
         if (Input.GetKeyUp (KeyCode.I)) //Checks what is in the inventory when I is pressed
         {
             CheckInventory(addedItems);
         }
         if (Input.GetKeyUp (KeyCode.Space)) //Waits for player to press space and performs the method generating a random number each time space is pressed
         {
             WeaponSearch ();//This is a method/funcion call
         }
     }
 
     void CheckInventory(string addedItems)//Creates inventory and places some items inside.
     {
         string [] inventory = new string[5]{"Ripped Tunic", "Old Boots", "Dagger", "Gold Ring", "null"};//Declares inventory list and what is in each slot
         foreach (string items in inventory) //Cycles through inventory
         {
             inventory[4] = addedItems;
             Debug.Log(items);
         }
     }
     void WeaponSearch()//This is a method/function definition
     {
         weapon = Random.Range (1, 5);//Generates random number between 1 and 5
         
         switch (weapon) 
         {
         case 1:
             weaponName = "Sword";
             UpdateInventory(weaponName);
             break;
             
         case 2:
             weaponName = "Axe";
             UpdateInventory(weaponName);
             break;
             
         case 3:
             weaponName = "Bow";
             UpdateInventory(weaponName);
             break;
             
         case 4:
             weaponName = "Dagger";
             UpdateInventory(weaponName);
             break;
             
         default:
             Debug.Log("You need a weapon!");
             break;
         }
     }
 
     void UpdateInventory (string weaponName)//Takes the names of the weapons 
     {
         addedItems = weaponName;
         CheckInventory (addedItems);
     }
 }