Interactable button UNITY

Question

I'm trying to make a simple condition:

If the value I have, is less than the price it costs the item, the button is disabled.

If the value I have, is greater than or equal to the price it costs the item the button is enabled and I can buy it.

But when I test, I have some problems.

First, if I have less than the item cost the button is enabled, and only when I click on it it is when it disables.

Second, if I have less than the item cost and I click on it it disables, but if I get enough to purchase the item, the button is not enabled again.

How do I to be checked these variables all the time? If I have enough the button is enabled if you do not have it disables.

Bellow my scrip:

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

    public class BuySkin : MonoBehaviour {

        public int price;
        public Button buyBee1;

        void OnEnable ()
        {
            //Register Button Events
            buyBee1.onClick.AddListener (() => buySkin (buyBee1));

        }


        public void buySkin(Button button)
        { 
            if (BeeCoinScore.coin >= price) {
                BeeCoinScore.coin -= price;
                buyBee1.interactable = false;

            }

            if (BeeCoinScore.coin < price) {
                buyBee1.interactable = false;
            }
        }

        void OnDisable ()
        {
            //Un-Register Button Events
            buyBee1.onClick.RemoveAllListeners ();

        }
    }

Answer 1

Try this out with some prefabs!

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

public class GameController : MonoBehaviour
{

    public int coins;
    private int spherePrice = 100, cubePrice = 50;

    public GameObject player;
    public GameObject[] availablePrefabs;
    public List<GameObject> mySkins;

    public Button btnSphere, btnCube;
    public Text txtSphere, txtCube;

    void Start ()
    {
        string serializedMySkins = PlayerPrefs.GetString ("skins", "");
        string serializedPlayer = PlayerPrefs.GetString ("player", "");

        // skins desserialization
        if (serializedMySkins == "")
            mySkins = new List<GameObject> ();
        else {
            var a = serializedMySkins.Split (',');
            for (int i = 0; i < a.Length; i++) {
                if (a [i] == "Sphere") {
                    mySkins.Add (availablePrefabs [0]);
                } 

                if (a [i] == "Cube") {
                    mySkins.Add (availablePrefabs [1]);
                } 
            }
        }

        // player desserialization
        if (serializedPlayer != "") {
            if (serializedPlayer == "Sphere") {
                player = availablePrefabs [0];
            } 

            if (serializedPlayer == "Cube") {
                player = availablePrefabs [1];
            } 
        } else {
            player = mySkins [0];
        }

        coins = PlayerPrefs.GetInt ("coins", 0);
        coins = 1000;
    }

    void Update ()
    {
        if (mySkins.Contains (availablePrefabs [0])) { 
            txtSphere.text = "Usar esfera";
        } else {
            btnSphere.interactable = coins >= spherePrice;
        }

        if (mySkins.Contains (availablePrefabs [1])) {
            txtCube.text = "Usar cubo";
        } else {
            btnCube.interactable = coins >= cubePrice;
        }
    }

    public void play ()
    {
        player = (GameObject)Instantiate (player, new Vector2 (0, 0), Quaternion.identity);
    }

    public void verifySkin (GameObject skinPrefab)
    {
        if (mySkins.Contains (skinPrefab)) {
            useSkin (skinPrefab);
        } else if (coins >= priceOf (skinPrefab)) {
            buySkin (skinPrefab, priceOf (skinPrefab));
        }
    }

    public void buySkin (GameObject skinPrefab, int price)
    {
        mySkins.Add (skinPrefab);
        coins -= price;

        string skinsHash = "";
        for (int i = 0; i < mySkins.Count; i++) {
            skinsHash += mySkins [i].name + ",";
        }

        Debug.Log (skinsHash);

        PlayerPrefs.SetInt ("coins", coins);
        PlayerPrefs.SetString ("skins", skinsHash);

        PlayerPrefs.Save ();
    }

    public void useSkin (GameObject skinPrefab)
    {
        player = skinPrefab;
        PlayerPrefs.SetString ("player", player.name);
        PlayerPrefs.Save ();
    }

    private int priceOf (GameObject skinPrefab)
    {
        if (skinPrefab == availablePrefabs [0])
            return spherePrice;
        else if (skinPrefab == availablePrefabs [1])
            return cubePrice;
        else
            return 0;
    }
}