Unity 新特性TryGetComponent

本文固定鏈接，轉載請評論點贊

一、起因：

沒啥，看到了，寫寫而已。

二、實現方式：

首先貼一下代碼：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class TryGetComponentTest : MonoBehaviour
{
    // Start is called before the first frame update
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        if(Input.GetKeyDown(KeyCode.Space))
        {
            Debug.Log("GetKeyDown KeyCode.Space");

            if (gameObject.transform.TryGetComponent<BoxCollider>(out BoxCollider boxC))
            {
                Debug.Log($"we get boxCollider:{boxC}");
            }
            else
            {
                Debug.Log("we not get boxCollider。");
            }

            if (gameObject.transform.TryGetComponent<Transform>(out Transform tran))
            {
                Debug.Log($"we get Transform:{tran}");
            }
            else
            {
                Debug.Log("we not get Transform。");
            }
        }
    }
}

運行結果如圖：

其次說明一下，這個方法必須要在2019.2以後才能用。

另外，據說是這個方法不會分配內存。原文如下：

Using TryGetComponent will not allocate memory in case it fails and is available since 2019.2. 

三、反編譯：

反編譯看了下c#層的代碼，如圖：

// UnityEngine.GameObject
[SecuritySafeCritical]
public unsafe bool TryGetComponent<T>(out T component)
{
	CastHelper<T> castHelper = default(CastHelper<T>);
	this.TryGetComponentFastPath(typeof(T), new IntPtr((void*)(&castHelper.onePointerFurtherThanT)));
	component = castHelper.t;
	return castHelper.t != null;
}

// UnityEngine.GameObject
[FreeFunction(Name = "GameObjectBindings::TryGetComponentFastPath", HasExplicitThis = true, ThrowsException = true), NativeWritableSelf]
[MethodImpl(MethodImplOptions.InternalCall)]
internal extern void TryGetComponentFastPath(Type type, IntPtr oneFurtherThanResultValue);