Drag, Drop and replace a specific Object

1) I have two objects in the plane



2) I am picking up my first object and adding it to inventory



3) I am dragging the object from inventory by using the mouse pointer and dropping it on the second object and the second object is replaced by the object dragged from the inventory.



4) The problem lies here when I am dragging the object from inventory and placing it somewhere else the first object moves to the original position from where I picked.

I want the second object to be replaced with the first one when I am dragging and dropping the first object on the second object ( which is working for me) but the first object should remain in the inventory rather than moving to the original position if I drag and drop the object at some other place (which the issue for me)

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. public class Photo : InventoryItemBase
5. {
6.     public GameObject replace;
7.     public Inventory inventory;
8.     public HUD Hud;
9.     // Start is called before the first frame update
10.     public override string Name
11.     {
12.         get
13.         {
14.             return "Photo";
15.         }
16.     }
17.     public override void OnDrop()
18.     {
19.         RaycastHit hit = new RaycastHit();
20.         Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
21.         replace = GameObject.FindGameObjectWithTag("replace");
22.         if (Physics.Raycast(ray, out hit, 1000))
23.         {
24.             //TODO item drop functionality on a fixed wall
25.        
26.             if (hit.collider.gameObject.CompareTag("replace"))
27.             {
28.                 gameObject.SetActive(true);
29.                 gameObject.transform.position = replace.gameObject.transform.position;
30.                 gameObject.transform.rotation = replace.gameObject.transform.rotation;
31.                 Destroy(replace.gameObject);
32.            
33.             }
34.             else
35.             {
36.                // Note sure what to add
37.             }
38.      
39.         }
40.     }
41. }

 

You want to use the hit variable to determine the location where to place the object.

Code (CSharp):

1. else
2. {
3.    yourObjFromInventory.transform.position = hit.point;
4. }

https://docs.unity3d.com/ScriptReference/RaycastHit-point.html

 

Thank you for your reply. No, I want the first object should move back to inventory if it doesn't hit the second object.

 

Then call your Pickup() method in the else?

 

I am using these specific lines of code, I am getting the result as expected but facing an error.

NullReferenceException: Object reference not set to an instance of an object
PhotnDrop () (at Assets/Scripts/Photo.cs:44)
Inventory.RemoveItem (IInventoryItem item) (at Assets/Scripts/Inventory.cs:44)
ItemDropHandler.OnDrop (UnityEngine.EventSystems.PointerEventData eventData) (at Assets/Scripts/ItemDropHandler.cs:27)
UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IDropHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/EventSystem/ExecuteEvents.cs:85)
UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/EventSystem/ExecuteEvents.cs:261)
UnityEngine.EventSystems.EventSystem:Update()

Code (CSharp):

1. else
2.             {
3.                 gameObject.SetActive(false);
4.                 IInventoryItem _item = gameObject.GetComponent<IInventoryItem>();
5.                 inventory.AddItem(_item);
6.                 _item.OnPickup();
7.                 Hud.CloseMessagePanel();
8.             }