Inheritance Confusion

Questions & Answers
1

I’m trying to inherit from an Enemy class to a Guard class but NOTHING IS INHERITING! How does this all work??? I’ve been at this for hours. I just keep coming up with UnsignedReferenceExceptions and things aren’t working. Here’s my code:

// Enemy.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class Enemy : MonoBehaviour 
{
	protected NavMeshAgent navMeshAgent = null;
	public List<GameObject> pathNodes = new List<GameObject>();
	protected int currentPathNodeIndex = 0;
	public float pathNodeDistanceThreshold = 1.0f;
	public GameObject player = null;
	public float aggroRadius = 5.0f;
	public int delayRange = 0;
	public float timer = 0.0f;

	// Use this for initialization
	void Start () 
	{
		delayRange = Random.Range(2, 10);
		navMeshAgent = gameObject.GetComponent<NavMeshAgent>();
		if (navMeshAgent == null)
		{
			navMeshAgent = gameObject.AddComponent<NavMeshAgent>();
		}
		
		if (pathNodes.Count <= 0)
		{
			Debug.LogError("This sytem requires that at least one path node blah blah blah....");
		}
		
		player = GameObject.FindWithTag("Player");
	}
	
	// Update is called once per frame
	void Update () 
	{
		if (player == null)
		{
			return;
		}

		if (navMeshAgent == null)
		{
			return;
		}
		
		if (pathNodes.Count <= 0)
		{
			return;
		}
	}
}

// Guard.cs

// Here, Guard isn't inheriting the Player so he can't find him
//Why? Shouldn't the Enemy grab the object with the tag, "Player" and therein allowing Guard to use it?

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class Guard : Enemy 
{
	// Use this for initialization
	void Start () 
	{

	}
	
	// Update is called once per frame
	void Update () 
	{
		if (Vector3.Distance(gameObject.transform.position, player.transform.position) <= aggroRadius)
		{
			navMeshAgent.destination = player.transform.position;
		}
		
		else
		{
			navMeshAgent.destination = pathNodes[currentPathNodeIndex].transform.position;
			if (Vector3.Distance(gameObject.transform.position, navMeshAgent.destination) <= pathNodeDistanceThreshold)
			{
				
				timer = timer + Time.deltaTime;
				if (timer >= delayRange)
				{
					timer = 0.0f;
					currentPathNodeIndex++;
					delayRange = Random.Range(2, 10);
				}
				
				if (currentPathNodeIndex >= pathNodes.Count)
				{
					currentPathNodeIndex = 0;
				}
			}
		}
	}
}

Why isn’t this working? Also, how do I put prefabs into lists at runtime? I need to do that so I can create new PathNodes and Enemy is able to grab those nodes and put them in the list. Any help would be appreciated. Inheritance just confuses me greatly…

2

Unity will only call the first Start() and Update() functions it find starting from the Child. So in your case the Start() and Update() in Guard will be used but not the ones in Enemy. Your player object never gets a value because the value is set in the Start() function in the Enemy which does not get called. A solution would be to add base.Start() and base.Update() in the Guard functions:

void Start () 
{
    base.Start();
}

void Update()
{
    base.Update();
}

Remember to change the Start() and Update() functions in Enemy to be either public or protected so that Guard has access to them.