Spawning a Ball going forward every 5 seconds error, help!

Questions & Answers
1

Alright so I made this script:

using UnityEngine;
using System.Collections;

public class CannonShots : MonoBehaviour {
    public Transform ballPos;
    public Rigidbody Ball;
   public  float timeMin = 1;
   public float timeMax = 3;
   public float forceAmount = 1500;

    void SpawnBall()
    {

        Rigidbody ballRigid;
        ballRigid = Instantiate(Ball, ballPos.position, ballPos.rotation) as Rigidbody;
        ballRigid.AddForce(ballPos.forward * forceAmount);
    }
    void Start() {
        float timeToSpawn = Random.Range(timeMin, timeMax);
        InvokeRepeating("SpawnBall", timeToSpawn, timeToSpawn);
    }
}

An error pops out saying NullReferenceException: Object reference not set to an instance of an object
CannonShots.SpawnBall () (at Assets/MyAssets/Scripts/CannonShots.cs:16) . I know what this error means but I can’t seem to figure out how to fix it. So can somebody please help me and explain what the error was and correct it? Thanks!

2

Have you assigned an object to the “ballPos and Ball” variables in the inspector ? I think the variables have a value of NULL. That is why it is called a NullReferenceException error.

3

@TheRealKuha

The following fixes your error(s) and adds some debugging

void SpawnBall()
{

    Rigidbody ballRigid;
    if ((Ball != null) && (ballPos != null))
    {
        ballRigid = Instantiate(Ball, ballPos.position, ballPos.rotation) as Rigidbody;
        if (ballRigid != null)
        {
            ballRigid.AddForce(ballPos.forward * forceAmount);
        }
        else
        {
            debug.LogWarning("The instantiated item does not contain a Rigidbody");
        }
    }
    else
    {
        if ((Ball == null)
        {
            debug.LogWarning("Ball has not been assigned. Please assign the Ball");
        }
        if (ballPos == null)
        {
            debug.LogWarning("ballPos has not been assigned. Please assign the ballPos");
        }
    }
}

Also if you want to spawn every 5 seconds you need to do it like this

InvokeRepeating("SpawnBall", timeToSpawn, 5);