I have a line:
private void OnTriggerEnter2D(Collider2D collider)
{
checkID = collider.GetComponent<PartInfo>().ID;
}
That PartInfo.cs:
using System;
using UnityEngine;
public class PartInfo : MonoBehaviour
{
[SerializeField] int id = 0;
GameObject parent = null;
public int ID { get { return id; } }
}
So I see this error on "checkID =" line. I don't understand why. Help me understand it, please :)
Yes, Thank you @olivier-jacot-descombes . There was no check for null. I just added
if(collider.GetComponent<PartInfo>() != null)
checkID =...
GetComponent twice here. Consider using pattern matching: if(collider.GetComponent<PartInfo>() is PartInfo pi) checkID = pi.ID; or an empty property pattern which also checks for "not null": if(collider.GetComponent<PartInfo>() is {} pi) checkID = pi.ID; or checkID = compareCollider.GetComponent<PartInfo>()?.ID ?? 0; to assign 0 when not part was found.
\$\endgroup\$
if (TryGetComponent(out PartInfo part) { checkID = part.ID; } instead. This lets you check for the existence of the component and take a reference if it exists in one concise step. It also avoids an extra allocation in edit mode (GetComponent generates a dummy object to stand in for the null for better error reporting in-editor).
\$\endgroup\$
compareCollideris null. 2. ComponentPartInfois null, i.e., the part info was not found. Either fix the underlying or write:checkID = compareCollider?.GetComponent<PartInfo>()?.ID ?? 0;\$\endgroup\$colliderand you check forcompareCollider. \$\endgroup\$