Reference to Null object Help beginner question

Questions & Answers
1

NullReferenceException: Object reference not set to an instance of an object
PlayerController.Update () (at Assets/Scripts/PlayerController.cs:23)
I got stuck while trying to follow this tutorial Mobile Swipe Detection [Tutorial][C#] - Unity 3d - YouTube
here is code:
using UnityEngine;
using System.Collections;

public enum SwipeDirection
{
	None = 0,
	Left = 1,
	Right = 2,
	Up = 4,
	Down = 8,

}
public class SwipeManager : MonoBehaviour {
	private static SwipeManager instance;
	public static SwipeManager Instance{get {return instance;}}
	public SwipeDirection Direction{set; get;}

	private Vector3 touchPosition;
	private float swipeResistanceX = 50.0f;
	private float swipeResistanceY = 100.0f;
	private void start(){
		instance = this;
	}
	private void Update()
	{
		Direction = SwipeDirection.None;
		if (Input.GetMouseButtonDown (0)) {
			touchPosition = Input.mousePosition;
		}
		if (Input.GetMouseButtonUp (0)) {
			Vector2 deltaSwipe = touchPosition - Input.mousePosition;
			if (Mathf.Abs (deltaSwipe.x) > swipeResistanceX) {
				Direction |= (deltaSwipe.x < 0) ? SwipeDirection.Right : SwipeDirection.Left;
			}
			if (Mathf.Abs (deltaSwipe.y) > swipeResistanceY) {
				Direction |= (deltaSwipe.y < 0) ? SwipeDirection.Up : SwipeDirection.Down;
			}
		}


	}
	public bool IsSwiping(SwipeDirection dir)
	{
		return (Direction & dir) == dir;
}
}

using UnityEngine;
using System.Collections;

public class PlayerController : MonoBehaviour {

	public float minSwipeDistY;

	public float minSwipeDistX;

	private Vector2 startPos;
	Animator animator;
	// Use this for initialization
	void Start () {
		animator = GetComponent<Animator> ();

	}
	
	// Update is called once per frame
	void Update () {
		if (animator.GetInteger ("Action") != 0){
			animator.SetInteger ("Action", 0);
		}
		if (SwipeManager.Instance.IsSwiping(SwipeDirection.Down)){
			animator.SetInteger ("Action", -1);
			}	


	}

}

Both scripts are applied to my player object if that helps

2

unity will not call start() but will call Start() - you need to pay special attention to the case of unity called functions.

make that change and see if the problem still occurs.