fps-citybuild-unity/Assets/Scripts/Building/BuildingBlueprint.cs

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

public abstract class BuildingBlueprint : MonoBehaviour
{
    public bool isColliding;
    public bool followMouse = true;
    public GameObject constructionPrefab;
    
    private GameObject terrain;


    Ray ray;

    public abstract void Init();
    public abstract void WhileColliding();
    public abstract void WhileNotColliding();

    private void Start()
    {
        terrain = GameObject.FindGameObjectWithTag("Terrain");
        Init();
    }


    //Collision
    public void OnCollisionEnter(Collision collision)
    {
        isColliding = true;
        
        Debug.Log("Colliding True");
    }
    public void OnCollisionStay(Collision collision)
    {
        isColliding = true;
        Debug.Log("Colliding True");
    }
    public void OnCollisionExit(Collision collision)
    {
        isColliding = false;
        Debug.Log("Colliding False");
    }

    //Placing
    public void Update()
    {
        if (followMouse)
        {
            //Following Mouse
            ray = Camera.main.ScreenPointToRay(Input.mousePosition);
            RaycastHit hitData;
            if (terrain.GetComponent<Collider>().Raycast(ray, out hitData, Mathf.Infinity))
            {
                transform.position = hitData.point;
            }
        }

        if (Input.GetMouseButtonDown(0) && !isColliding)
        {
            Instantiate(constructionPrefab, transform.position, transform.rotation);
            Destroy(this.gameObject);
        }

        if (isColliding)
        {
            WhileColliding();
        }
        else
        {
            WhileNotColliding();
        }
    }

}