Question

So, I have a dictionary called Potions. I need to check if a key in potions has the same name as an object passed as an argument. Now I’m able to do that but I can’t figure out how to add a value to that particular key if the item object and the key have the same name. This code works fine for the first instance of an object. But when I add another instance object with the same name as a key, I get a key not found exception. I understand that the 2 objects wont be the same.How can I extract the object reference inside the dictionary? Or is there another way?

public static void addItem(Potion item)
 {
    if (Potions.Count >0)
    {
        foreach(KeyValuePair<Potion,int> pair in Potions)
        {
            if (pair.Key.itemName == item.itemName)
            {
            containsItem = true;
            }   
        }
        if (containsItem)
        {
        Potions[item] += 1;
        Debug.Log (Potions[item]);
        containsItem = false;
        }
        else
            {       
            Potions.Add(item,1);
            }
    }
    else
    {
    Potions.Add (item,1);
    }

    foreach(KeyValuePair<Potion,int> pair in Potions)
    {
        Debug.Log (pair.Key.itemName + " : " + pair.Value);
    }
 }

Answer 1

You can override Equals and GetHashCode, but that might have other implications. Instead, you can use an IEqualityComparer when you create the dictionary, like so:

class Potion {
    public string Name;
    public int Color;
}

class PotionNameEqualityComparer : IEqualityComparer<Potion> {
    public bool Equals(Potion p1, Potion p2) {
        return p1.Name.Equals(p2.Name);
    }
    public int GetHashCode(Potion p1) {
        return p1.Name.GetHashCode();
    }
}

void Main() {
    var d = new Dictionary<Potion, int>(new PotionNameEqualityComparer());
    var p1 = new Potion() { Name = "Health", Color = 1 };
    var p2 = new Potion() { Name = "Health", Color = 2 };
    d.Add(p1, 1);
    d[p2]++; // works, and now you have two health potions. 
             // Of course, the actual instance in the dictionary is p1; 
             // p2 is not stored in the dictionary.    
}