Component類
1. 官方定義
class in UnityEngine/Inherits from:Object/Implemented in:UnityEngine.CoreModule
屬於UnityEngine命名空間下，繼承自Object類，與之前的Object類和GameObject類一樣屬於核心模塊。
2. 官方描述
Base class for everything attached to GameObjects.
Note that your code will never directly create a Component. Instead, you write script code, and attach the script to a GameObject. See Also: ScriptableObject as a way to create scripts that do not attach to any GameObject.
此類要對比下GameObject類，GameObject類是場景中所有實體的基類，而Component類是掛載在實體身上所有組件的基類，官方強調腳本是一個組件，但是腳本不可以直接掛載到實體上，當然官方介紹的ScriptableObject類是一種不附加到實體上的方法，後續再做介紹。
3. 屬性
gameObject：The game object this component is attached to. A component is always attached to a gameobject.
語法：public GameObject gameObject;
獲取自身物體，Component類比較特殊，除了gameobject這個屬性，其他的與GameObject類的屬性和方法相同，我這邊全部裂解液出來，再在最後說明原因。
tag：The tag of this game object.
transform：The Transform attached to this GameObject.
4. 共有方法
BroadcastMessage：Calls the method named methodName on every MonoBehaviour in this game object or any of its children.
CompareTag：Is this game object tagged with tag ?
GetComponent：Returns the component of Type type if the game object has one attached, null if it doesn’t.
GetComponentInChildren：Returns the component of Type type in the GameObject or any of its children using depth first search.
GetComponentInParent：Returns the component of Type type in the GameObject or any of its parents.
GetComponents：Returns all components of Type type in the GameObject.
GetComponentsInChildren：Returns all components of Type type in the GameObject or any of its children.
GetComponentsInParent：Returns all components of Type type in the GameObject or any of its parents.
SendMessage：Calls the method named methodName on every MonoBehaviour in this game object.
SendMessageUpwards：Calls the method named methodName on every MonoBehaviour in this game object and on every ancestor of the behaviour.
TryGetComponent：Gets the component of the specified type, if it exists.
以上就是官方2019.3版本Component類的全部內容，看過第三期教程的朋友會發現屬性和方法和GameObject類基本相同，這是爲什麼呢，因爲Unity在設計時，通過GameObject類創建場景實體，而實體的屬性和功能通過組件來完成，而組件時掛載在實體上的，所以Component類給出gameobject屬性（注意此處爲小寫），gameobject時Component類的屬性，很多朋友在學習API時對於Object，GameObject以及gameobject發生混淆，Object和GameObject時類，具有父子關係，他們同屬於UnityEngine命名空間下，而gameobject屬於Component類的一個屬性，Component類和Object也是一種父子關係，Component類和GameObject類在設計上屬於同級關係，但是基於Unity的設計，在實現上，GameObjec類是實現的基礎，而Component類是實現的行爲外觀，這裏還要提一個Object類，根據Unity結構，他不屬於UnityEngine命名空間下，而是System.Object，屬於最終基類，因爲我們用UNity寫的腳本現在都是C#語言，這裏只做概述不做具體介紹。所以，我們可以通過組件訪問掛載物體，從而實現訪問，示例如下：
using UnityEngine;
public class NewBehaviourScript : MonoBehaviour
{
void Start()
{
GameObject go = new GameObject();
go.AddComponent(typeof(Rigidbody));
Rigidbody rg = go.GetComponent(typeof(Rigidbody))as Rigidbody;
rg.gameObject.AddComponent(typeof(Mesh));
}
}
後面官方給的是繼承的內容，此處不做概述，本期教程到此結束，歡迎大家在評論區給出意見和指正，謝謝瀏覽。