Using FindObjectofType and FindObjectOfTypeAll Unity methods - unity3d

Question

GameObject[] rm = FindObjectsOfTypeAll(typeof(RoadMovement)) as GameObject[];
if (Input.GetKeyDown (KeyCode.LeftArrow))
{
foreach(GameObject r in rm) //objectRefrence not set to instance of an object error here
{
var bounds1 = r.renderer.bounds;
var bounds2 = player.renderer.bounds;
Transform roadtransform = r.transform;
if(bounds1.Intersects(bounds2))
{
if (this.transform.position.x > r.renderer.bounds.min.x)
this.transform.position = new Vector3 (this.transform.position.x - 0.6f, this.transform.position.y, this.transform.position.z);
}
}
}
What is difference between FindObjectOfType and FindObjectOfTypeAll? I want to get all the objects that have RoadMovement script attached to them.I understand the error: Object reference not set to an instance but not sure how to fix this?

Answer 1

First problem: FindObjectsOfTypeAll has been deprecated for quite some time, and is no longer documented at all in current versions of Unity. Because you're comparing objects in the scene, it looks like you want Object.FindObjectsOfType.
Second problem: the lookup call you're making doesn't return an array of GameObjects, so the as operator will return null when the cast fails. You mentioned that RoadMovement is a behavior script you wrote. That implies that every RoadMovement has a GameObject, but not that every RoadMovement is a GameObject.
This is also why you're getting an InvalidCastException that you're asking about. Understand your return types and you will understand the error.
Recent Unity versions even added a generic version of FindObjectsOfType:
RoadMovement[] roadMovements = Object.FindObjectsOfType<RoadMovement>();
foreach (RoadMovement roadMovement in roadMovements) {
GameObject myGameObject = roadMovement.gameObject;
//do something
}