Button SetActive

I'm trying to make a button that has SetActive=false when an object A collides with an object B but i'm can't figure out how.

 

public UnityEngine.UI.Button F;

void Start()
{

F = GetComponent<UnityEngine.UI.Button>();
}

private void OnCollisionEnter2D(Collision2D collision)
{
if (collision.gameObject.CompareTag("Wall"))
{
F.gameObject.SetActive(false);
}
}


This is not working

 

If this is a script for a component on the Button object, try:

// public UnityEngine.UI.Button F;

void Start()
{

// F = GetComponent<UnityEngine.UI.Button>();
}

private void OnCollisionEnter2D(Collision2D collision)
{
if (collision.gameObject.CompareTag("Wall"))
{
// F.gameObject.SetActive(false);
gameObject.SetActive(false);
}
}

 

can you explain why this works?i think there isn't much difference between F.gameObject.SetActive(false); and gameObject.SetActive(false); (the difference is that the first one can't be used but the second one can be used .it is really amazing!)Thank you !