SyncDictionary

A SyncDictionary is an associative array containing an unordered list of key, value pairs. Keys and values can be any supported mirror type. By default we use .Net Dictionary which may impose additional constraints on the keys and values.

SyncDictionary works much like SyncLists: when you make a change on the server the change is propagated to all clients and the appropriate Actions are invoked. Only deltas are transmitted.

Usage

SyncDictionary must be declared readonly and initialized in the constructor.

Note that by the time you wire up the Action handlers, the dictionary will already be initialized, so they will not get invoked for the initial data, only updates.

Simple Example

using System.Collections.Generic;
using UnityEngine;
using Mirror;

public enum Slots : byte { head, body, feet, hands }

public struct Item
{
    public string name;
    public int hitPoints;
    public int durability;

    public Item(string name, int hitPoints, int durability)
    {
        this.name = name;
        this.hitPoints = hitPoints;
        this.durability = durability;
    }

    public override string ToString()
    {
        return $"name={name} hitPoints={hitPoints} durability={durability}";
    }
}

public class SyncDictionaryExample : NetworkBehaviour
{
    public readonly SyncDictionary<Slots, Item> Equipment = new SyncDictionary<Slots, Item>();

    public override void OnStartServer()
    {
        Equipment[Slots.head] = new Item("Helmet", 10, 20);
        Equipment[Slots.body] = new Item("Epic Armor", 50, 50);
        Equipment[Slots.feet] = new Item("Sneakers", 3, 40);
        Equipment[Slots.hands] = new Item("Sword", 30, 15);
    }

    public override void OnStartClient()
    {
        // Add handlers for SyncDictionary Actions
        Equipment.OnAdd += OnItemAdded;
        Equipment.OnSet += OnItemChanged;
        Equipment.OnRemove += OnItemRemoved;
        Equipment.OnClear += OnDictionaryCleared;

        // OnChange is a catch-all event that is called for any change
        // to the dictionary. It is called after the specific events above.
        // Strongly recommended to use the specific events above instead!
        Equipment.OnChange += OnDictionaryChanged;

        // Dictionary is populated before handlers are wired up so we
        // need to manually invoke OnAdd for each element.
        foreach (Slots key in Equipment.Keys)
            Equipment.OnAdd.Invoke(key);
    }

    public override void OnStopClient()
    {
        // Remove handlers when client stops
        Equipment.OnAdd -= OnItemAdded;
        Equipment.OnSet -= OnItemChanged;
        Equipment.OnRemove -= OnItemRemoved;
        Equipment.OnClear -= OnDictionaryCleared;
        Equipment.OnChange -= OnDictionaryChanged;
    }

    void OnItemAdded(Slots key)
    {
        Debug.Log($"Element added {key} {Equipment[key]}");
    }

    void OnItemChanged(Slots key, Item oldValue)
    {
        Debug.Log($"Element changed {key} from {oldValue} to {Equipment[key]}");
    }

    void OnItemRemoved(Slots key, Item oldValue)
    {
        Debug.Log($"Element removed {key} {oldValue}");
    }

    void OnDictionaryCleared()
    {
        // OnDictionaryCleared is called before the dictionary is actually cleared
        // so we can iterate the dictionary to get the elements if needed.
        foreach (KeyValuePair<Slots, Item> kvp in Equipment)
            Debug.Log($"Element cleared {kvp.Key} {kvp.Value}");
    }

    // OnDictionaryChanged is a catch-all event that is called for any change
    // to the dictionary. It is called after the specific events above.
    //
    // NOTE: It's strongly recommended to use the specific events above instead!
    //
    // For OP_ADD, the value param is the NEW entry.
    // For OP_SET, the value param is the OLD entry.
    // For OP_REMOVE, the value param is the OLD entry.
    // For OP_CLEAR, the value param is null / default.
    void OnDictionaryChanged(SyncDictionary<Slots, Item>.Operation op, Slots key, Item value)
    {
        switch (op)
        {
            case SyncDictionary<Slots, Item>.Operation.OP_ADD:
                // value is the new entry
                Debug.Log($"Element added {key} {value}");
                break;

            case SyncDictionary<Slots, Item>.Operation.OP_SET:
                // value is the old entry
                Debug.Log($"Element set {key} from {value} to {Equipment[key]}");
                break;

            case SyncDictionary<Slots, Item>.Operation.OP_REMOVE:
                // value is the old entry
                Debug.Log($"Element removed {key} {value}");
                break;

            case SyncDictionary<Slots, Item>.Operation.OP_CLEAR:
                // value is null / default
                // we can iterate the dictionary to get the elements if needed.
                foreach (KeyValuePair<Slots, Item> kvp in Equipment)
                    Debug.Log($"Element cleared {kvp.Key} {kvp.Value}");
                break;
        }
    }
}

By default, SyncDictionary uses a Dictionary to store it's data. If you want to use a different IDictionary implementation such as SortedList or SortedDictionary, then use SyncIDictionary and pass the dictionary instance you want it to use. For example:

public class ExamplePlayer : NetworkBehaviour
{
    public readonly SyncIDictionary Equipment = 
        new SyncIDictionary(new SortedList());
}