how would i go about allowing me to change the tag of an object on runtime with OnCollisionEnter2D

Question

private void OnCollisionEnter2D(Collision2D collision)
{
    while (onWeapon == false && collision.gameObject.tag == "Weapon")
    {
        onWeapon = true;
    } 
    
    
    
    if (onWeapon == true && Input.GetKey(KeyCode.E))
    {
        currentPos = gameObject.transform.position;
        collision.transform.position = currentPos;
        collision.transform.parent = player.transform;
        collision.tag = "WeaponHeld";
    }

    
}

i cant change the object tag on runtime with "OnEnterCollision2D" but the same line worked when i used "OnTriggerEnter2D"

Answer 1

First of all what is your while loop good for? Anyway there will be only exactly one single iteration so just make it

if(!onWeapon && collision.gameObject.CompareTag("Weapon"))
{
    onWeapon = true;
}

Then aCollision2D is a data container struct with specific data about the collision and itself has no tag.

The gameObject you collide with has

collision.gameObject.tag = "WeaponHeld";

Or since you are using the transform anyway you can also use that one

var otherTransform = collision.transform;
otherTransform.position = currentPos;
otherTransform.parent = player.transform;
otherTransform.tag = "WeaponHeld";

because it has the property tag as well which forwards to the according gameObject.tag .

---

Why did it work in OnTriggerEnter2D ?

Because there as a parameter you don't get aCollision2D struct but rather a Collider2D component reference.

And as just mentioned also for Transform the base class Component has the property tag which basically simply forwards to the according gameObject.tag (see source code ).