A few C# problems.

Questions & Answers
1

Below are two scripts, one for summoning a projectile (goes on the gun), and the other for collisions which goes on the projectile.
The first problem is “Cannot cast from source type to destination type.” While i have googled the problem none of the answers explain what is wrong but rather give a specific fix. Full debug.log
InvalidCastException: Cannot cast from source type to destination type.
WeaponScript.ShootingFunc () (at Assets/Script/WeaponScript.cs:43)
WeaponScript.Update () (at Assets/Script/WeaponScript.cs:23)

The second problem i’m having is that every time i fire the Ammo var is supposed to go down by one, however it does not. Also i have a simple delay between shots and this is also not working, is this due to the invalidCastException?

This is the code for the weapon and projectile instancing

using UnityEngine;
using System.Collections;

public class WeaponScript : MonoBehaviour {
	public Rigidbody projectile;
	public int ammoLeft = 0;
	public bool isWeaponCycling;
	public float weaponCycling; 

	void Start () {

		isWeaponCycling = false;
		weaponCycling = 5.0f;

	}

	void Update () {
	if (Input.GetButtonDown ("Fire1")) 
		{
			if (isWeaponCycling == false)
			{
			ShootingFunc();
			}else
			{
			Debug.Log("Cannot Fire at this time");
			}

		}
		if (isWeaponCycling)
		{
			weaponCycling -= Time.deltaTime;
			if (weaponCycling < 0)
			{
				isWeaponCycling = false;
				weaponCycling = 5.0f;
			}
		}
	}

	void ShootingFunc ()
	{
		Rigidbody bullet = (Rigidbody)Instantiate(projectile, transform.position, transform.rotation);
		isWeaponCycling = true;
		ammoLeft -= 1;
		Debug.Log ("You have " + ammoLeft + " rounds left");

			if (ammoLeft == 0)
			{
			Debug.Log ("Horey shit guys no ammo left");
			}
		}
}

The other script goes on the actual projectile.

public class ProjectileScript : MonoBehaviour {
	public int projectileSpeed = 500;
	public float timeTillDeath = 10;


		void FixedUpdate () {
				rigidbody.AddForce (Vector3.forward * 10);
		}

	void Update () {
		transform.Translate (Vector3.forward * Time.deltaTime * 600);
		timeTillDeath = timeTillDeath - Time.deltaTime;

		if (timeTillDeath < 0) 
			{
			Destroy (gameObject);
			}
	}

	void OnCollisionEnter(Collision col){
		if (col.gameObject.CompareTag("Enemy")){
			col.gameObject.SendMessage("HealthAdj", -10, SendMessageOptions.DontRequireReceiver);
		}
		Destroy(gameObject); // bullet suicides after hitting anything
	}
}

Thanks in advance, this has been bugging me all morning.

2

Your trying to Instantiate a RigidBody, if your providing a location / rotation then Unity is expecting a GameObject.

Change → public Rigidbody projectile;
To → public GameObject projectile;

And then drag the projectile prefab on to the projectile property.