Renderer.materials not working in void update()

this is my code and i get this error every frame

NullReferenceException: Object reference not set to an instance of an object
wheelThreeScript.Start () (at Assets/Scripts/wheelScripts/wheelThreeScript.cs:20)

using UnityEngine;
using System.Collections;

public class wheelThreeScript : MonoBehaviour {

public int wheelSymbol;
Renderer rend;
SymbolPicker symbolPicker;
public Material coin, coins, damage, heart, skull, jackpot;

// Use this for initialization
void Start () {
	Renderer renderer = GetComponent<Renderer> ();
	GameObject slotMachine = GameObject.FindGameObjectWithTag ("slotMachine");
	symbolPicker = slotMachine.GetComponent<SymbolPicker> ();

	rend.material = coin;

// Update is called once per frame
void Update () {
	wheelSymbol = symbolPicker.wheelThreeSymbol;

	if (wheelSymbol == 1)
		rend.material = coin;
	if (wheelSymbol == 2)
		rend.material = coins;
	if (wheelSymbol == 3)
		rend.material = heart;
	if (wheelSymbol == 4)
		rend.material = damage;
	if (wheelSymbol == 5)
		rend.material = skull;
	if (wheelSymbol == 6)
		rend.material = jackpot;


You defined a private class member variable “rend”:

Renderer rend;

However you never initialize it. In start you have this line:

Renderer renderer = GetComponent<Renderer> ();

which defines a local variable inside start which is initialized to the Renderer component of that gameobject, but you never use that local variable. I think you want to do

rend = GetComponent<Renderer> ();

You’ve not pasted the code correctly which it makes the line numbers tricky to follow, but I believe the line in question is:

wheelSymbol = symbolPicker.wheelThreeSymbol;

which suggests that the following line is returning null:

symbolPicker = slotMachine.GetComponent<SymbolPicker> ();

which suggests that the GO you’re assigning to the symbolPicker variable doesn’t have a SymbolPicker component.