Editor’s note

I always misunderstood the object injection of unity. I thought it would be successful if I specified the object bound by the script in component, but I found that this was a wrong understanding

Unity error – nullreferenceexception

Error code

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

public class SliderLightBehaviourScript : MonoBehaviour {

	public GameObject light;

	// Use this for initialization
	void Start () {
		//this.light = GameObject.Find ("Directional Light");
	}
	
	// Update is called once per frame
	void Update () {
		
	}

	public void OnDrag(float value){
		Debug.LogError (value);
		this.light.transform.rotation = Quaternion.Euler (new Vector3(value,0.y,0));
	}
}

Error report

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

Problem understanding

Objects created in GameObject’s scene are not bound to code objects. Confirm that GameObject cannot be bound through component

Find the content of official documents through inquiry

To get GameObject object, you must use GameObject. Find or related functions. You cannot use other methods

Solution code

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

public class SliderLightBehaviourScript : MonoBehaviour {

	public GameObject light;

	// Use this for initialization
	void Start () {
		this.light = GameObject.Find ("Directional Light");
	}
	
	// Update is called once per frame
	void Update () {
		
	}

	public void OnDrag(float value){

		Vector3 light_rotation = light.transform.rotation.eulerAngles;


		Debug.LogError (value);
		this.light.transform.rotation = Quaternion.Euler (new Vector3(value,light_rotation.y,0));
	}
}