using UnityEngine;

public abstract class Singleton<T> : MonoBehaviour where T : Component
{
    // 保存当前类型唯一的正式实例。
    private static T instance;

    /// <summary>取得当前类型的唯一实例。</summary>
    public static T Instance
    {
        get
        {
            if (instance == null)
            {
                instance = FindObjectOfType<T>();

                if (instance == null)
                {
                    GameObject obj = new GameObject();
                    obj.name = typeof(T).Name;
                    instance = obj.AddComponent<T>();
                }
            }

            return instance;
        }
    }

    /// <summary>保留第一个实例，并移除后来出现的重复对象。</summary>
    protected virtual void Awake()
    {
        if (instance == null)
        {
            instance = this as T;
            DontDestroyOnLoad(gameObject);
        }
        else
        {
            Destroy(gameObject);
        }
    }
}