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);
	}
}

Make sure your script is attached to an object for it to work. If you’re sure about that, try debugging a message when the Input is read. like:
Debug.Log(“Spacebar pressed.”);
or just a print.