Mirror/doc/Articles/Guides/Sync/SyncDictionary.md
2020-10-02 13:56:20 -05:00

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# SyncDictionary
A SyncDictionary is an associative array containing an unordered list of key, value pairs. Keys and values can be any [supported mirror type](../DataTypes.md). By default we use .Net [Dictionary](https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2?view=netcore-3.1) which may impose additional constraints on the keys and values.
SyncDictionary works much like [SyncLists](SyncLists.md): when you make a change on the server the change is propagated to all clients and the Callback is called. Only deltas are transmitted.
## Usage
Add a field to your NetworkBehaviour class fo type `SyncDictionary<Key, Value>`. For example:
> Note that by the time you subscribe to the callback, the dictionary will already be initialized, so you will not get a call for the initial data, only updates.</p>
>Note SyncDictionaries must be initialized in the constructor, not in Startxxx(). You can make them readonly to ensure correct usage.
## Simple Example
```cs
using UnityEngine;
using Mirror;
public struct Item
{
public string name;
public int hitPoints;
public int durability;
}
public class ExamplePlayer : NetworkBehaviour
{
public readonly SyncDictionary<string, Item> Equipment = new SyncDictionary<string, Item>();
public override void OnStartServer()
{
Equipment.Add("head", new Item { name = "Helmet", hitPoints = 10, durability = 20 });
Equipment.Add("body", new Item { name = "Epic Armor", hitPoints = 50, durability = 50 });
Equipment.Add("feet", new Item { name = "Sneakers", hitPoints = 3, durability = 40 });
Equipment.Add("hands", new Item { name = "Sword", hitPoints = 30, durability = 15 });
}
public override void OnStartClient()
{
// Equipment is already populated with anything the server set up
// but we can subscribe to the callback in case it is updated later on
Equipment.Callback += OnEquipmentChange;
}
void OnEquipmentChange(SyncDictionary<string, Item>.Operation op, string key, Item item)
{
// equipment changed, perhaps update the gameobject
Debug.Log(op + " - " + key);
}
}
```
By default, SyncDictionary uses a [Dictionary](https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2?view=netcore-3.1) to store it's data. If you want to use a different `IDictionary` implementation such as [SortedList](https://docs.microsoft.com/en-us/dotnet/api/system.collections.sortedlist?view=netcore-3.1) or [SortedDictionary](https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.sorteddictionary-2?view=netcore-3.1), then use `SyncIDictionary<Key,Value>` and pass the dictionary instance you want it to use. For example:
```cs
public class ExamplePlayer : NetworkBehaviour
{
public readonly SyncIDictionary<string, Item> Equipment =
new SyncIDictionary<string, Item>(new SortedList<string, Item>());
}
```