Why dosent this work?!

im having problems with this code for an enemy AI to follow me. this is not meant to attack me yet and i do have a sphere collider on the enemy(this is also set as trigger) ive placed my script on the enemy too.

this is the code:

using UnityEngine;
using System.Collections;

public class BasicAI : MonoBehaviour {

private NavMeshAgent agent;
private Transform PlayerTransform;

private void start()
{
agent = GetComponent<NavMeshAgent>();
}

private void OnTriggerEnter(Collider target)
{
if (target.tag == "Player")
{
PlayerTransform = target.transform;
agent.SetDestination(PlayerTransform.position);
}
}
}


error:
NullReferenceException: object reference not set to an instance of an object



can anyone help me??!!

 

Please use proper code tags when posting code.

Function names are case sensitive. You have "private void start()" which should just be "void Start()". Please use the following.

Code (csharp):

1. using UnityEngine;
2.  
3. public class BasicAI : MonoBehaviour
4. {
5.    private NavMeshAgent agent;
6.    private Transform target;
7.  
8.    void Start()
9.    {
10.      this.agent = this.GetComponent<NavMeshAgent>();
11.      if (this.agent == null)
12.      {
13.        throw new UnityException("Missing NavMeshAgent!");
14.      }
15.    }
16.  
17.    void OnTriggerEnter(Collider target)
18.    {
19.      if (target.CompareTag("Player"))
20.      {
21.        this.target = target.transform;
22.        this.agent.SetDestination(this.target.position);
23.      }
24.    }
25. }

 

thx for the help! it works yipee

 

One tip to add:
Use with caution, though (see later posts from jimroberts why)
To avoid checking that the correct component (in this case NavMeshAgent) is also attached to the GameObject, you can require it - see here for the API documentation.
That way if you add your BasicAI script to a GameObject, it will automatically add NavMeshAgent if one is not present.

 

This could be a really bad idea if you are expecting the values of your component to be set via the inspector. In my opinion it is better to throw an exception describing which component is missing so you can go configure it correctly. Using the RequireComponent attribute feels like you're just sweeping the problem under the rug.

 

Depends on what you're used to I suppose. Your method is definitely safer.
RequireComponent does come handy if you're not relying on inspector set values and are chaining components (since AddComponent will also add all RequiredComponents if used from code side). That way if I'm building objects from code and I need f.e. to change a rock into a unit, I can AddComponent<EnemyAI> and chain other needed components from there with default values, adjusting only what's needed.

Either way, I agree that this can be abused and/or misused and I probably shouldn't have added it to a beginner level topic. I'll edit to add warning there.