//MenuGUI.css
using UnityEngine;
using System.Collections;

public class MenuGUI : MonoBehaviour {

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {

    }

    void OnGUI() {
        GUI.Box (new Rect (10, 10, 100, 200), "Weapons");
        //GUI.Box (new Rect (Screen.width - 200, Screen.height - 200, 400, 400), "Inventory");

        if (GUI.Button (new Rect (15, 35, 90, 20), "Sniper")) {
            WieldWeapon.PickUpWeapon("sniper");
            Debug.Log("Sniper retrieved");
        }
    }
}




//WieldWeapon.css
using UnityEngine;
using System.Collections;

public class MenuGUI : MonoBehaviour {

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {

    }

    void OnGUI() {
        GUI.Box (new Rect (10, 10, 100, 200), "Weapons");
        //GUI.Box (new Rect (Screen.width - 200, Screen.height - 200, 400, 400), "Inventory");

        if (GUI.Button (new Rect (15, 35, 90, 20), "Sniper")) {
            WieldWeapon.PickUpWeapon("sniper");  //  <---------------------- Error here
            Debug.Log("Sniper retrieved");
        }
    }
}


//Erreur: Assets/Scripts/MenuGUI.cs(21,37): error CS0120: An object reference is required to access non-static member `WieldWeapon.PickUpWeapon(string)'