Adding Force to an instantiated object when it spawns?

Hi, having trouble wrapping my head around achieving this:

I’m making a game where there are 4 spawn points on the right side of the screen.

I have an array of objects(1 in it at the moment)
I also have an array of spawnpoints (4)

My aim is to have the object move to the left side of the screen slowly until it reaches a trigger.

My current script is below.

My objects instantiate fine, and spawn in the right spots (grabs a random object from the “Junk” Gameobject array, spawns it in one of the 4 spawnpoints from the SpawnPoints Transform array.

How do I manipulate the spawned object to move in said motion?

I figure I need to make it a rigidbody, and use rigidbody.addforce, but i’m missing something!

The error message is:

SpawnItems.SpawnJunk() (Line 41): NullReferenceException: Object Reference not set to an instance of an object.

What am I forgetting to pass?

“JunkInstance.AddForce (SpawnPoints[spawnindex].forward * 800);”

Junkinstance is our instanced rigidbody. AddForce demands a vector3, Spawnpoints is our transform array, and spawnindex is a stored transform. .forward returns a vector3, so surely I’m not missing anything? 0_O. This isn’t making sense to me :expressionless:

using UnityEngine;
using System.Collections;

public class SpawnItems : MonoBehaviour {

	// indexes Junk into an array
	// indexes SpawnPoints into an array
	// Spawns random Junk obj from a random SpawnPoint.
	// Assign object to move down the lane it spawned in.

	public Transform[] SpawnPoints; // array of spawnpoints, linked with transform in editor. this is also beginning of our "lanes".
	public float SpawnTime = 1.5f; // time between spawn "waves"
	public GameObject[] Junk; // Array of Junk Objects

	// Use this for initialization
	void Start () {
		InvokeRepeating ("SpawnJunk", SpawnTime, SpawnTime);
		// invokes SpawnJunk method after $SpawnTime seconds, then again every $SpawnTime seconds.

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

	void SpawnJunk()
		int spawnindex = Random.Range (0, SpawnPoints.Length);
			// set index number of the array randomly

		int objectIndex = Random.Range (0, Junk.Length);
			// object Index = random number in range of between 0 & GameObject[] Junk.Length

		Rigidbody JunkInstance;
		JunkInstance = Instantiate (Junk[objectIndex], SpawnPoints [spawnindex].position, SpawnPoints [spawnindex].rotation) as Rigidbody;
		// Instantiates a random Junk obj to a random spawnpoint, following the spawnpoint's rotation.

		JunkInstance.AddForce (SpawnPoints[spawnindex].forward * 800);
		// BROKEN!

JunkInstance.AddForce (SpawnPoints[spawnindex].forward * 800);

needs to be

JunkInstance.GetComponent<RigidBody>().AddForce (SpawnPoints[spawnindex].forward * 800);

As you try to use the AddForce function with a GameObject, but you have to use it with a rigidbody that is on a gameobject.

The result of the Instantiate method is a GameObject because the object given to it is a GameObject. Casting it with a “as” will be null.

So JunkInstance will always be null.

Either use a array of rigid body or cast to GameObject then get the rigid body component.