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UnityObject 空引用检查小测试

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Classes deriving from Unity. Object inherit equality operators that change the behaviour of the == and != operators.
While these operators will perform standard . NET reference equality, if comparing one side to null, these operators will call native code to check if the underlying native engine object is still alive.

这段解释来自Rider的提示：
https://github.com/JetBrains/resharper-unity/wiki/Avoid-null-comparisons-against-UnityEngine.Object-subclasses

UnityEngine 底层是C++写的，所以说，其实我们对UnityObject的空引用检查都会再深入到里面C++那一层去再检查，这个检查是比较消耗的。
之前曾经遇到因为使用了 ?. 语法糖而导致的 this 指针为null的奇妙bug，大概也是因为这个原因。

现在的公司是做手游的，大家对性能都比较看重，不过我也真的好奇这个检查到底有多消耗，决定跑一跑试试。

Test Case

因为是做手游，随意干脆就在手机上测试好了。
大概是这样的环境:
Unity 2019.4 LTS

移动设备这边是
Google Pixel Verzion(俺穷买美版)
Android 9 (已获取Root权限)

TestCase 这边其实我都是瞎弄的。

分别进行三种测试：
Unity Object 的空引用检查；
POCO Object 的空引用检查；
bool 的直接检查；(因为我觉得这是一个代替Unity Object空引用检查的一个方法

每一种检查都有检查到true和false的两种情况，并循环跑多次。

然后，上代码！

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namespace TempCheckTest
{

    public class TempObjA
    {
        private int m_tempNum = 56;
    }

    public class NullCheckTester : MonoBehaviour
    {
        // unity obj null check
        private Transform m_emptyTransform = null;
        private Transform m_selfTransform = null;

        // poco obj null check
        private TempObjA m_emptyObjA = null;
        private TempObjA m_objA = null;

        // bool check
        private bool m_boolTrue = true;
        private bool m_boolFalse = true;

        [Header("test")]
        public int m_checkTimes = 100000;

        [Header("UI side")]
        public UnityEngine.UI.Text m_outPutText = null;
        public UnityEngine.UI.Button m_doUnityObjTestButton = null;
        public UnityEngine.UI.Button m_doPocoObjTestButton = null;
        public UnityEngine.UI.Button m_doBoolTestButton = null;

        public UnityEngine.UI.InputField m_inputField = null;

        [Button("init awake")]
        public void InitTester()
        {
            m_emptyTransform = null;
            m_selfTransform = this.transform;

            m_emptyObjA = null;
            m_objA = new TempObjA();

            m_boolTrue = true;
            m_boolFalse = false;

            m_outPutText.text = string.Empty;

            m_doUnityObjTestButton.onClick.RemoveAllListeners();
            m_doPocoObjTestButton.onClick.RemoveAllListeners();
            m_doBoolTestButton.onClick.RemoveAllListeners();

            m_doUnityObjTestButton.onClick.AddListener(DoUnityObjNullCheckTest);
            m_doPocoObjTestButton.onClick.AddListener(DoPOCOObjNullCheckTest);
            m_doBoolTestButton.onClick.AddListener(DoBoolObjNullCheckTest);

            m_inputField.onValueChanged.RemoveAllListeners();
            m_inputField.onValueChanged.AddListener(OnInputNumberChanged);
            m_checkTimes = 100000;
            m_inputField.text = m_checkTimes.ToString();
        }

        [Button("do unity.object null check test")]
        public void DoUnityObjNullCheckTest()
        {
            System.Diagnostics.Stopwatch watcher = new System.Diagnostics.Stopwatch();
            watcher.Start();
            for (int i = 0; i < m_checkTimes; i++)
            {
                if (null == m_emptyTransform) {}

                if (null == m_selfTransform) {}
            }
            watcher.Stop();

            string outPut = $"do unity.object null check test 2*{m_checkTimes} cost {watcher.ElapsedMilliseconds}ms";
            m_outPutText.text = outPut;
            Debug.Log(outPut);
        }

        [Button("do poco object null check test")]
        public void DoPOCOObjNullCheckTest()
        {
            System.Diagnostics.Stopwatch watcher = new System.Diagnostics.Stopwatch();
            watcher.Start();
            for (int i = 0; i < m_checkTimes; i++)
            {
                if (null == m_emptyObjA) {}

                if (null == m_objA) {}
            }
            watcher.Stop();

            string outPut = $"do poco object null check test 2*{m_checkTimes} cost {watcher.ElapsedMilliseconds}ms";
            m_outPutText.text = outPut;
            Debug.Log(outPut);
        }

        [Button("do bool check test")]
        public void DoBoolObjNullCheckTest()
        {
            System.Diagnostics.Stopwatch watcher = new System.Diagnostics.Stopwatch();
            watcher.Start();
            for (int i = 0; i < m_checkTimes; i++)
            {
                if (m_boolFalse) {}

                if (m_boolTrue) {}
            }
            watcher.Stop();

            string outPut = $"do bool check test 2*{m_checkTimes} cost {watcher.ElapsedMilliseconds}ms";
            m_outPutText.text = outPut;
            Debug.Log(outPut);
        }

        public void OnInputNumberChanged(string arg0)
        {
            int result = 0;
            if (!Int32.TryParse(arg0, out result))
                result = Int32.MaxValue;

            m_checkTimes = result;
        }

        #region mono method

        private void Reset()
        {
            InitTester();
        }

        private void Awake()
        {
            InitTester();
        }

        private void OnEnable()
        {
            this.enabled = false;
        }

        #endregion

    }

}

Test Result

分别进行10w次和100w次测试看看结果。

10w次:
Unity Object null check 4~7ms
POCO Object null check 0ms
bool check 0ms

100w次:
Unity Object null check 45~60ms
POCO Object null check 3~4ms
bool check 2ms

当检测数量非常多的时候，Unity Object 空引用检查的性能消耗比其他两个大了很多很多。现在的项目里大部分东西其实都是POCO的。
似乎把UnityObject Destroy之后再手动把变量置空是个好习惯（