默认情况下Public是暴露给Unity，protect/private是不暴露给Unity的，但有时候想让外部引用，又不想暴露给Unity，怎么办？

• 对Unity隐藏，使用[HideInInspector]

  using UnityEngine;
  using System.Collections;

  public class NewBehaviourScript:MonoBehaviour{
  [HideInINspector]//起作用
  public int bb = 2;
  }

• 对Unity暴露，使用[SerializeField]

  using UnityEngine;
  using System.Collections;

  public class NewBehaviourScript:MonoBehaviour{
  [SerializeField]//起作用
  private int bb = 2;
  }

• 结构体要暴露给Unity,使用[System.Serializable]

  using UnityEngine;
  using System.Collections;

  [System.Serializabel]//起作用
  public class CustomStruct
  {
  }
  public class NewBehaviourScript:MonoBehaviour{
  public CustomStruct Cus;//引用后即可
  }