實現Unity對Dictionary的序列化

若有嘗試過想在unity的inspector檢視面板中像List或者數組那樣可以編輯Dictionary變量的童鞋應該知道，Dictionary變量不會出現在inspector中，unity並不會直接序列化Dictionary類型，但實際上unity有提供接口使之可能：

unity doc: http://docs.unity3d.com/ScriptReference/ISerializationCallbackReceiver.OnBeforeSerialize.html。

注意其中的This interface should be used very carefully. Unity's serializer usually runs on the non main thread, while most of the Unity API can only be called from the main thread.

請慎用該方法，它不是線程安全的。

using UnityEngine;
using System.Collections.Generic;

/// Usage:
/// 
/// [System.Serializable]
/// class MyDictionary : SerializableDictionary<int, GameObject> {}
/// public MyDictionary dic;
///
[System.Serializable]
public class SerializableDictionary<TKey, TValue> : Dictionary<TKey, TValue>, ISerializationCallbackReceiver
{
    // We save the keys and values in two lists because Unity does understand those.
    [SerializeField]
    private List<TKey> _keys;
    [SerializeField]
    private List<TValue> _values;

    // Before the serialization we fill these lists
    public void OnBeforeSerialize()
    {
　　　　　　//官方例子有誤，去掉     
　　　　}

    // After the serialization we create the dictionary from the two lists
    public void OnAfterDeserialize()
    {
        this.Clear();
        int count = Mathf.Min(_keys.Count, _values.Count);
        for (int i = 0; i < count; ++i)
        {
            this.Add(_keys[i], _values[i]);
        }
    }
}