Check values of multiple gameobjects

I'm not claiming this to be the best method, but it is a method to go about.

• Numbers.unitypackage download

When you click one button, remember that as the button that was clicked. When you click another button, swap value with the previouly clicked button and the most recently clicked button. Additionally you can perform an animation to give more feedback if you want. I did not include that in my example.

Number.cs

 using System;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.Events;
 using UnityEngine.UI;
 
 public class Number : MonoBehaviour
 {
     [Serializable]
     public class NumberEvent : UnityEvent<int> { }
     public Text text;
     public NumberEvent onValueChanged;
     public int Value
     {
         get { return value; }
         set
         {
             if (this.value == value)
                 return;
             this.value = value;
             Refresh();
             onValueChanged.Invoke(value);
         }
     }
 
     [SerializeField]
     private int value;
     private static Number selected;
 
     void Awake()
     {
         Refresh();
     }
 
     void Refresh()
     {
         text.text = value.ToString();
     }
 
     // Bind button to call this during On Click
     public void OnClick()
     {
         if (!selected)
         {
             selected = this;
         }
         else
         {
             Swap(selected, this);
             Deselect();
         }
     }
 
     public static void Swap(Number a, Number b)
     {
         int tmp = a.Value;
         a.Value = b.Value;
         b.Value = tmp;
     }
 
     public static int Sum(IEnumerable<Number> numbers)
     {
         int sum = 0;
         foreach (var number in numbers)
             sum += number.Value;
         return sum;
     }
 
     // Could be useful to call if you pause the game or enter other menues etc.
     public static void Deselect()
     {
         selected = null;
     }
 }

To calculate score, just loop through all the connected numbers and add their values together.

ConnectedNumbers.cs

 using UnityEngine;
 using UnityEngine.UI;
 
 public class ConnectedNumbers : MonoBehaviour
 {
     public Number[] connected;
     public Text text;
 
     void Awake()
     {
         foreach (var number in connected)
             number.onValueChanged.AddListener(ConnectedValueChanged);
 
         Refresh();
     }
 
     void ConnectedValueChanged(int unused)
     {
         Refresh();
     }
 
     void Refresh()
     {
         text.text = Number.Sum(connected).ToString();
     }
 }