Duplicated objects are not working 'per instance' when I intended them to do

Question

using UnityEngine;

public class LinkEnd : MonoBehaviour
{
    public GameObject linkTarget;
    private PointEffector2D effector;
    private CircleCollider2D contact;
    private AimSystem aimer;

    private float distFromLink = .2f;
    public bool connected;

    private void Start()
    {
        aimer = GetComponent<AimSystem>();
    }

    private void Update()
    {
        SyncPosition();

        ReactToInput();
    }

    public void ConnectLinkEnd(Rigidbody2D endRB)
    {
        HingeJoint2D joint = GetComponent<HingeJoint2D>();

        if (GetComponent<HingeJoint2D>() == null)
        {
            joint = gameObject.AddComponent<HingeJoint2D>();
        }

        joint.autoConfigureConnectedAnchor = false;
        joint.connectedBody = endRB;
        joint.anchor = Vector2.zero;
        joint.connectedAnchor = new Vector2(0f, -distFromLink);
    }

    private void SyncPosition()
    {
        if (linkTarget != null)
        {
            if (Vector2.Distance(transform.position, contact.transform.position) <= 0.1f)
            {
                connected = true;
                effector.enabled = false;
                contact.usedByEffector = false;
            } 
        }

        if (connected)
        {
            GetComponent<Rigidbody2D>().isKinematic = true;
            GetComponent<Rigidbody2D>().position = linkTarget.transform.position;
        }
        else
            GetComponent<Rigidbody2D>().isKinematic = false;
    }

    private void ReactToInput()
    {
        if (Input.GetKeyUp(KeyCode.Mouse0) || Input.GetKey(KeyCode.Mouse1))
        {
            connected = false;
        }
    }

    public void OnTriggerEnter2D(Collider2D collision)
    {
        if (collision.GetComponent<PointEffector2D>() != null)
        {
            connected = true;
            linkTarget = collision.gameObject;
            effector = linkTarget.GetComponent<PointEffector2D>();
            contact = linkTarget.GetComponent<CircleCollider2D>();
        }
    }

    public void OnTriggerExit2D(Collider2D collision)
    {
        connected = false;
        contact.usedByEffector = true;
        effector.enabled = true;
    }
}

This is an object that pins its position to another mobile object on collision, and it's supposed to stay that way until it's 'detached' by player action. It's working almost fine, but it's not working 'per instance.' Whether this object is a prefab or not, ReactToInput() is affecting all instances of it unlike how I wanted. I'm missing some per instance specification here and I'm not seeing where.

Any suggestion will help and be appreciated!

++ The method ReactToInput() is triggered by key inputs. I wanted this method to be called when Player's attack 'method' happens which are bound to those key inputs, but I did what I've done only because I couldn't find an elegant way to execute it otherwise, and am really hoping there's a better way rather than using tags or GetComponent to specific object since it's supossed to affect other objects as well.

Answer 1

These methods are what you are looking for.

/// <summary>
/// OnMouseDown is called when the user has pressed the mouse button while
/// over the GUIElement or Collider.
/// </summary>
void OnMouseDown()
{
    Debug.Log("Hi!");

}

/// <summary>
/// OnMouseUp is called when the user has released the mouse button.
/// </summary>
void OnMouseUp()
{
    Debug.Log("Bye!");
}

MonoBehaviour provides many event callbacks other than Update(), and these two are some of them. The full list of event callbacks you can use for MonoBehaviour is explained in the official Monobehaviour page.

There are two methods for OnMouseUp():

OnMouseUp is called when the user has released the mouse button.

OnMouseUpAsButton is only called when the mouse is released over the same GUIElement or Collider as it was pressed.

The GameObject your script is attached to is requires to have GUIElement or Collider as described in the manual page to use these functions.

If you do not want to use these methods, you could alternatively write your own custom InputModule, raycast to the mouse position on the screen to find which object is clicked, and send MouseButtonDown() event to a clicked GameObject.

I had to implement a custom input module to do this plus a couple of other stuff and I assure you writing custom InputModules is a headache.

---

EDIT:

If many different classes need to be notified when something happens, and who listens to such cases is unknown, event is a good option.

If you are using events, each event listener class such as LinkEnd is responsible to register and remove itself to such event.

Below is an example of how you could achieve this behaviour:

class Player
{
    public delegate void OnSkillAFiredListener(object obj, SkillAFiredEventArgs args);
    public static event OnSkillAFiredListener SkillAPressed = delegate { };
    // ...
}

class LinkEnd
{
    void OnEnable()
    {
        Player.SkillAPressed += WhatToDoWhenSkillAFired;
    }

    void OnDisable()
    {
        Player.SkillAPressed -= WhatToDoWhenSkillAFired;
    }

    void OnDestroy()
    {
        Player.SkillAPressed -= WhatToDoWhenSkillAFired;
    }

    public void WhatToDoWhenSkillAFired(object obj, SkillAFiredEventArgs args)
    {
        // get info from args
        float someInfo = args.someInfo

        // do something..
        Bark();
    }

    // ...
}

It's necessary to deregister from the event in both OnDisable() and OnDestory() to avoid memory leaks (some claim such memory leaks are very minor).

Look for Observer and Publisher/Subscriber pattern to learn more about these approaches. It may not be very related to your case, but the Mediator Pattern is something that's often compared with the Observer Pattern so you might be interested to check it as well.