ArgumentException: An item with the same key has already been added. Key: Point

I have this error with the below script and I have no idea how to fix it
PelletScript.CreateNodes () (at Assets/Scripts/PelletScript.cs:77)
PelletScript.Start () (at Assets/Scripts/PelletScript.cs:37)

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class PelletScript : MonoBehaviour
6. {
7.     private static Dictionary<Point, Node> nodes;
8.     private Point neighboursPos;
9.  
10.     public List<Node> neighbours = new List<Node>();
11.     public List<Vector2> validDirections;
12.  
13.     public static PelletScript Instance { get; set; }
14.  
15.     public Point GridPosition { get; private set; }
16.  
17.     public Vector2 WorldPosition
18.     {
19.         get
20.         {
21.             return new Vector2(transform.position.x + (GetComponent<SpriteRenderer>().bounds.size.x / 2), transform.position.y - (GetComponent<SpriteRenderer>().bounds.size.y / 2));
22.         }
23.     }
24.  
25.     public bool Walkable { get; set; }
26.  
27.     private void Awake()
28.     {
29.         Instance = this;
30.     }
31.  
32.     // Start is called before the first frame update
33.     void Start()
34.     {
35.         if (nodes == null)
36.         {
37.             CreateNodes();
38.         }
39.  
40.         PelletScript currentPellet = this;
41.  
42.         for (int x = -1; x <= 1; x++)
43.         {
44.             for (int y = -1; y <= 1; y++)
45.             {
46.                 //Debug.Log(x + ";" + y);
47.                 neighboursPos = new Point(currentPellet.GridPosition.X - x, currentPellet.GridPosition.Y - y);
48.                 //Debug.Log(neighboursPos.X + " " + neighboursPos.Y);
49.                 if (MapManager.instance.InBounds(neighboursPos) && MapManager.instance.AllPellets[neighboursPos].Walkable && neighboursPos != currentPellet.GridPosition)
50.                 {
51.                     Node neighbour = nodes[neighboursPos];
52.                     neighbours.Add(neighbour);
53.                 }
54.             }
55.         }
56.  
57.         validDirections = new List<Vector2>(neighbours.Count);
58.  
59.         for (int i = 0; i < neighbours.Count; i++)
60.         {
61.             Node currentNeighbour = neighbours[i];
62.             Vector3 currNPos = new Vector3(currentNeighbour.GridPosition.X, currentNeighbour.GridPosition.Y, 0);
63.             Vector2 tempVector = currNPos - transform.localPosition;
64.  
65.             validDirections[i] = tempVector.normalized;
66.         }
67.     }
68.  
69.     private static void CreateNodes()
70.     {
71.         //Instantiates the dictionary
72.         nodes = new Dictionary<Point, Node>();
73.  
74.         //Run through all pellets in the game
75.         foreach (PelletScript pellet in MapManager.instance.AllPellets.Values)
76.         {
77.             nodes.Add(pellet.GridPosition, new Node(pellet));
78.         }
79.     }
80.  
81.     public void Setup(Point gridPos, Vector3 worldPos)
82.     {
83.         Walkable = true;
84.         this.GridPosition = GridPosition;
85.         transform.position = worldPos;
86.         MapManager.instance.AllPellets.Add(gridPos, this);
87.     }
88. }

 

It means that you already have added a node with the same grid Position. Since grid Position is the key which you use to retrieve dict items, adding the new key value pair would no longer guarantee that all keys are unique, and you wouldn't be able to to retrieve all values. Hence the error.

-ch

 

I don't see where you're setting up the

Point

values in each

GridPosition

, or even the definition of

Point

to see how it would be compared. But let's assume that all that is done and compares can be done.

A

Dictionary<KeyType, ValueType>

can only have one

ValueType

element at a given

KeyType

place. If you have an entry at

Point(4, 3)

, you cannot add another entry at

Point(4, 3)

without removing the old one first. If you attempt to do so, the

ArgumentException

is thrown.

 

this are the point and node scripts

Code (CSharp):

1. using UnityEngine;
2.  
3. public struct Point
4. {
5.     public int X { get; set; }
6.  
7.     public int Y { get; set; }
8.  
9.     public Point (int x, int y)
10.     {
11.         this.X = x;
12.         this.Y = y;
13.     }
14.  
15.     public static bool operator == (Point first, Point second)
16.     {
17.         return first.X == second.X && first.Y == second.Y;
18.     }
19.  
20.     public static bool operator != (Point first, Point second)
21.     {
22.         return first.X != second.X || first.Y != second.Y;
23.     }
24. }
25.  

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Node
6. {
7.     public Point GridPosition { get; private set; }
8.  
9.     public PelletScript PelletRef { get; private set; }
10.  
11.     public Node(PelletScript pelletRef)
12.     {
13.         this.PelletRef = pelletRef;
14.         this.GridPosition = pelletRef.GridPosition;
15.     }
16. }
17.