I want the key to appear after collecting all the coins

i am making a simple 2d platformer game and i really need some help. I have coins and the player needs to collect all of them. I also have a key and a door, door opens right after player gets the key. Here is the problem: Key is visible all the time but i want it to be visible once the player colllects all the coins so player can get the key and end the chapter. How can i make this happen?

This is my players code:
`

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

public class Player : MonoBehaviour
{

    private Rigidbody2D myRigidbody;
    private Animator anim;
    private int score;
    public Text totalscore;
    [SerializeField]
    private GameObject playerhaskey, dooropened;
    [SerializeField]
    private int speed;
    private bool lookright;

    void Start()
    {
        myRigidbody = GetComponent<Rigidbody2D>();
        anim = GetComponent<Animator>();
        score = 0;
        lookright = true;
    }

    void Update()
    {
        float horizontal = Input.GetAxis("Horizontal");
        movements(horizontal);
        changedirection(horizontal);
    }


    private void movements(float horizontal)
    {
        anim.SetFloat("Walk", Mathf.Abs(horizontal));
        myRigidbody.velocity = new Vector2(horizontal * speed, myRigidbody.velocity.y);
    }

    private void changedirection(float horizontal)
    {
        if (horizontal > 0 && !lookright || horizontal < 0 && lookright)
        {
            lookright = !lookright;
            Vector3 direction = transform.localScale;
            direction.x *= -1;
            transform.localScale = direction;
        }
    }

    void OnTriggerEnter2D(Collider2D collider)
    {
        if (collider.gameObject.tag == "gold")
        {
            collider.gameObject.SetActive(false);
            score = score + 1;
            changescore(score);
        }
    }

    void OnCollisionEnter2D(Collision2D other)
    {
        if (other.gameObject.tag == "key")
        {
            other.gameObject.SetActive(false);
            playerhaskey.SetActive(true);
            dooropened.SetActive(true);
        }
    }

    void changescore(int count)
    {
        totalscore.text = count.ToString();

    }
}

`

>Solution :

First of all as a side note I would use the same technique for both key and coins. You could have a single OnTriggerEnter2D handle both.

Then I assume all coins are enabled at the beginning and apparently all have a tag gold anyway so you could simply do something like e.g.

private int totalCoinsRequired;

private GameObject key;

private void Start()
{
    // find the key object
    key = GameObject.FindWithTag("key");

    // find all coins -> amount needed to unlock key
    totalCoinsRequired = GameObject.FindGameObjectsWithTag("gold").Length;

    // initially hide the key
    key.SetActive(false);
}

...

void OnTriggerEnter2D(Collider2D collider)
{
    if (collider.CompareTag("gold"))
    {
        collider.gameObject.SetActive(false);
        score += + 1;
        changescore(score);

        // if score reaches required amount unlock key
        if(score >= totalCoinsRequired)
        {
            key.SetActive(true);
        }
    }
}