GameObject类
1. 官方定义
class in UnityEngine/Inherits from:Object/Implemented in:UnityEngine.CoreModule
属于 UnityEngine命名空间下的类，继承于Object类，和Object类一样是UnityEngine.CoreModule下的核心模块类。
2.官方描述
Base class for all entities in Unity Scenes.
Note: Many variables in the GameObject class have been removed. To access, for example GameObject.renderer in csharp use GetComponent() instead.
See Also: Component.
上述说明GameObject类是Unity场景中所有实体的基类，也就是说Unity场景中物体的创建要通过此类来进行创建。官方后面给了注释，是因为API的弃用，主要是因为4.0X到5.0X以后版本的巨大改变，此处我们不需考虑，后面的代码我会用最新的写法进行解释，按照新版本API的写法用即可，同样的Compent类也有很大改变。
3.属性
activeInHierarchy：Defines whether the GameObject is active in the Scene.
语法：public bool activeInHierarchy;
该属性表示物体的激活状态，当然涉及到子类和父类物体，这里不做解释，我们结合下面的activeSelf属性进行对比解释。
activeSelf：The local active state of this GameObject. (Read Only)
语法：public bool activeSelf;
activeSelf表示物体自身的激活状态，与activeInHierarchy不同的是，activeSelf不受父物体的影响，如果有一个子类和父类物体，父类和子类都激活时，activeSelf和activeInHierarchy输出则都为true，如果父类不激活而子类激活，则我们查看子类激活状态时，activeSelf为true而activeInHierarchy为false，演示如下：
using UnityEngine;
public class ACTest : MonoBehaviour
{
public GameObject Parent, Child;
void Start()
{
Parent.SetActive(false);
Child.SetActive(true);
Debug.Log(Parent.activeSelf);
Debug.Log(Parent.activeInHierarchy);
Debug.Log(Child.activeSelf );
Debug.Log(Child.activeInHierarchy);
}
}
上述代码定义了两个物体，我们需要在场景中创建两个物体，并关联为父子物体，再通过SetActive方法将父物体关闭，子物体激活，注意定义public对象后要在Inspector面板中对物体进行获取，最后进行控制台打印结果，可得我们上述结论。
isStatic：Gets and sets the GameObject’s StaticEditorFlags.
语法：public bool isStatic;
该属性表示物体是否为静态，该属性比较好理解，此处不做代码演示，Unity为了对性能进行优化时需要对场景进行烘培，而烘培对象必须设置为静态，一般都是在场景编辑时在Inspector面板进行勾选，当然你可通过控制台打印输出查看物体是否为静态。
layer：The layer the game object is in.
语法：public int layer;
该属性为int型变量，表示游戏物体所在的层，层可用于从摄影机进行选择性渲染或忽略光线投射。Unity可生成32层，默认使用8层，当然也可以根据情况进行更改，我们在Inspector面板可以设置和查看，演示如下：
using UnityEngine;
public class LyTest : MonoBehaviour
{
void Start()
{
GameObject go = new GameObject();
Debug.Log(go.layer);
}
}
scene：Scene that the GameObject is part of.
语法：public SceneManagement.Scene scene;
该属性表示游戏对象所属的场景，因为使用SceneManagement.Scene类进行创建，我们在SceneManagement类教程中在做分析。
tag：The tag of this game object.
语法：public string tag;
该方法表示物体标签，Unity官方强调不要在Awake方法或OnValidate方法设置标签，因为组件唤醒的顺序不确定，可能会出现覆盖等情况，导致消息无法传递，该属性比较简单，不做赘述。
transform：The Transform attached to this GameObject.
语法：public Transform transform;
该属性为Transform类定义，用于表示游戏对象的转换方位等，演示如下：
```csharp
using UnityEngine;
public class TFTest : MonoBehaviour
{
void Start()
{
gameObject.transform.Translate(1, 1, 1);
}
}
4.构造方法
GameObject：Creates a new game object, named name.
语法：public GameObject();
public GameObject(string name);
public GameObject(string name, params Type[] components);
```csharp
using UnityEngine;
public class GOTest : MonoBehaviour
{
void Start()
{
GameObject go = new GameObject("hello",typeof(Rigidbody));
}
}
5.公有方法
AddComponent：Adds a component class named className to the game object.
语法：public Component AddComponent(Type componentType);
public Component AddComponent(Type componentType);
将名为className的组件类添加到游戏对象中，注意没有RemoveComponent()方法，删除组件用Destroy方法，该方法重载，可通过Type传递参数或者是使用泛型，演示如下：
using UnityEngine;
public class ATTest : MonoBehaviour
{
// Start is called before the first frame update
void Start()
{
GameObject go = new GameObject();
go.AddComponent(typeof(Rigidbody)) ;
go.AddComponent<MeshCollider>();
}
}
BroadcastMessage：Calls the method named methodName on every MonoBehaviour in this game object or any of its children.
语法：public void BroadcastMessage(string methodName, object parameter = null, SendMessageOptions options = SendMessageOptions.RequireReceiver);
该方法表示向自身或者子物体传送消息，有三个参数，methodName是方法名，parameter为对象，SendMessageOptions.RequireReceiver为没有接收到消息是否打印报错，演示如下：
public class _2 : MonoBehaviour
{
// Start is called before the first frame update
void Start()
{
gameObject.BroadcastMessage("Receive");
}
}
using UnityEngine;
public class _3 : MonoBehaviour
{
private void Receive()
{
Debug.Log("receive");
}
}
此处注意要在场景中设置父子物体，因该方法跟SendMessage和SendMessageUpwards有关联，所以设置三层物体，也就是父子孙关系，分别命名_01，_02，_03，对应相应代码块。
CompareTag：Is this game object tagged with tag ?
语法：public bool CompareTag(string tag);
该方法用于判断物体的标签是否为目标标签，并返回一个bool值，参数为string类型的tag，演示如下：
using UnityEngine;
public class CTTest : MonoBehaviour
{
void Start()
{
GameObject go = new GameObject();
if(go.CompareTag("Player"))
{
Debug.Log("true");
}
else
{
Debug.Log("false");
}
}
}
GetComponent：Returns the component of Type type if the game object has one attached, null if it doesn’t.
语法：public Component GetComponent(Type type);
public T GetComponent();
public Component GetComponent(string type);
该方法重载，有三种写法，用于访问获取组件，在Unity中只有拿到了组件，才可以对组件进行访问，演示如下：
using UnityEngine;
public class GTTest : MonoBehaviour
{
void Start()
{
GameObject go = new GameObject();
go.AddComponent(typeof(Rigidbody));
go.GetComponent(typeof(Rigidbody));
go.GetComponent<Rigidbody>();
go.GetComponent("Rigidbody");
}
}
GetComponentInChildren：Returns the component of Type type in the GameObject or any of its children using depth first search.
语法：public Component GetComponentInChildren(Type type);
public Component GetComponentInChildren(Type type, bool includeInactive);
public T GetComponentInChildren(bool includeInactive = false);
该方法重载，用于获取子物体组件，includeInactive表示将物体设置为激活状态，如果不设置为激活状态，将无法获取组件，演示如下：
using UnityEngine;
public class GetComponentInChildrenExample : MonoBehaviour
{
// Disable the spring on the first HingeJoint component found on any child object
void Start()
{
HingeJoint hinge = gameObject.GetComponentInChildren(typeof(HingeJoint)) as HingeJoint;
if (hinge != null)
hinge.useSpring = false;
else
{
// Try again, looking for inactive GameObjects
HingeJoint hingeInactive = gameObject.GetComponentInChildren(typeof(HingeJoint), true) as HingeJoint;
if (hingeInactive != null)
hingeInactive.useSpring = false;
}
}
}
上述代码，摘自官方示例。
GetComponentInParent：Returns the component of Type type in the GameObject or any of its parents.
语法：public Component GetComponentInParent(Type type);
public T GetComponentInParent();
该方法用于获取父物体的组件，有关Component获取的方法大致相同，代码示例将全部摘自官方示例：
using UnityEngine;
using System.Collections;
public class GetComponentInParentExample : MonoBehaviour
{
// Disable the spring on the first HingeJoint component found on any parent object
void Start()
{
HingeJoint hinge = gameObject.GetComponentInParent(typeof(HingeJoint)) as HingeJoint;
if (hinge != null)
hinge.useSpring = false;
}
}
GetComponents：Returns all components of Type type in the GameObject.
语法：public Component[] GetComponents(Type type);
public T[] GetComponents();
public void GetComponents(Type type, List results);
public void GetComponents(List results);
该方法用于得到一组同样类型的组件，返回的是一个数组或者是链表，演示如下：
// Disable the spring on all HingeJoints in this game object
using UnityEngine;
public class GetComponentsExample : MonoBehaviour
{
// Disable the spring on all HingeJoints in this game object
void Start()
{
Component[] hingeJoints;
hingeJoints = GetComponents(typeof(HingeJoint));
foreach (HingeJoint joint in hingeJoints)
joint.useSpring = false;
}
}
// Disable the spring on all HingeJoints in this game object
using UnityEngine;
using System.Collections.Generic;
public class GetComponentsExample : MonoBehaviour
{
// Disable the spring on all HingeJoints in this game object
void Start()
{
// Disable the spring on all HingeJoints in this game object
List<Component> hingeJoints = new List<Component>();
GetComponents(typeof(HingeJoint), hingeJoints);
foreach (HingeJoint joint in hingeJoints)
joint.useSpring = false;
}
}
GetComponentsInChildren：Returns all components of Type type in the GameObject or any of its children.
语法：public Component GetComponentInChildren(Type type);
public Component GetComponentInChildren(Type type, bool includeInactive);
public T GetComponentInChildren(bool includeInactive = false);
获取子物体的一组组件，注意物体要处于激活状态，演示如下：
using UnityEngine;
public class GetComponentInChildrenExample : MonoBehaviour
{
// Disable the spring on the first HingeJoint component found on any child object
void Start()
{
HingeJoint hinge = gameObject.GetComponentInChildren(typeof(HingeJoint)) as HingeJoint;
if (hinge != null)
hinge.useSpring = false;
else
{
// Try again, looking for inactive GameObjects
HingeJoint hingeInactive = gameObject.GetComponentInChildren(typeof(HingeJoint), true) as HingeJoint;
if (hingeInactive != null)
hingeInactive.useSpring = false;
}
}
}
GetComponentsInParent：Returns all components of Type type in the GameObject or any of its parents.
语法：public Component[] GetComponentsInParent(Type type, bool includeInactive = false);
public T[] GetComponentsInParent();
public T[] GetComponentsInParent(bool includeInactive);
public void GetComponentsInParent(bool includeInactive, List results);
该方法用于返回父物体的一组组件，为数组或者链表，注意设置物体的额激活状态,演示如下：
using UnityEngine;
public class GetComponentsInParentExample : MonoBehaviour
{
void Start()
{
Component[] hingeJoints;
hingeJoints = GetComponentsInParent(typeof(HingeJoint));
if (hingeJoints != null)
{
foreach (HingeJoint joint in hingeJoints)
joint.useSpring = false;
}
else
{
// Try again, looking for inactive GameObjects
Component[] hingesInactive = GetComponentsInParent(typeof(HingeJoint), true);
foreach (HingeJoint joint in hingesInactive)
joint.useSpring = false;
}
}
}
SendMessage：Calls the method named methodName on every MonoBehaviour in this game object.
语法：public void SendMessage(string methodName, object value = null, SendMessageOptions options = SendMessageOptions.RequireReceiver);
该方法表示向自身发送消息，有三个参数，与BroadcastMessage一样，value表示要传递给被调用方法的可选参数值，演示如下：
using UnityEngine;
public class _2 : MonoBehaviour
{
void Start()
{
gameObject.SendMessage("Receive");
}
}
using UnityEngine;
public class _0 : MonoBehaviour
{
private void Receive()
{
Debug.Log("receive");
}
}
SendMessageUpwards：Calls the method named methodName on every MonoBehaviour in this game object and on every ancestor of the behaviour.
语法：public void SendMessageUpwards(string methodName, object value = null, SendMessageOptions options = SendMessageOptions.RequireReceiver);
该方法表示向自身及父类发送消息，参数同SendMessage，演示如下：
using UnityEngine;
public class _2 : MonoBehaviour
{
private void Start()
{
gameObject.SendMessageUpwards("Receive");
}
}
using UnityEngine;
public class _1 : MonoBehaviour
{
private void Receive()
{
Debug.Log("receive");
}
}
SetActive：Activates/Deactivates the GameObject, depending on the given true or false value.
语法：public void SetActive(bool value);
该方法用于激活物体，前面已经介绍过，不再赘述。
TryGetComponent：Gets the component of the specified type, if it exists.
语法：public bool TryGetComponent（Type type，out Component compomemt）
public bool TryGetComponent(out T component);
该方法表示查找获取指定类型的组件，与GameObject.GetComponent相比，若查找组件不存在时将不会在编辑器中进行分配，演示如下：
using UnityEngine;
public class TryGetComponentExample : MonoBehaviour
{
void Start()
{
if (gameObject.TryGetComponent(typeof(HingeJoint), out Component component))
{
component.name = "My Hinge";
}
}
}
6.静态方法
CreatePrimitive：Creates a game object with a primitive mesh renderer and appropriate collider.
语法：public static GameObject CreatePrimitive(PrimitiveType type);
用于根据指定类型创建物体，该方法如果在使用时没有引用MeshFilter、meshfrenderer和BoxCollider或spherecollier组件，会出现创建失败的情况，避免的建议方法是声明这些类型的私有属性，剥离系统将识别它们的用途，并将它们包含在构建中，因此不会删除这些组件，示例如下：
using UnityEngine;
public class Example : MonoBehaviour
{
// Create a plane, sphere and cube in the Scene.
void Start()
{
GameObject plane = GameObject.CreatePrimitive(PrimitiveType.Plane);
}
}
Find：Finds a GameObject by name and returns it.
语法：public static GameObject Find(string name);
按名称查找游戏对象并返回它，此函数只返回活动的游戏对象，如果找不到名称为的GameObject，则返回null，如果名称包含“/”字符，则它将像路径名称一样遍历层次结构。出于性能原因，建议不要每帧都使用此功能。相反，在启动时将结果缓存到成员变量中。或者使用GameObject.FindWithTag。如果你想找到一个子游戏对象，通常使用Transform.find更容易；如果游戏运行时有多个场景，那么Find将搜索所有场景。
演示如下：
using UnityEngine;
public class FTest : MonoBehaviour
{
public GameObject go;
void Start()
{
GameObject gb =new GameObject（"Cube"）;
go = GameObject.Find("Cube");
}
}
FindGameObjectsWithTag：Returns an array of active GameObjects tagged tag. Returns empty array if no GameObject was found.
语法：public static GameObject[] FindGameObjectsWithTag(string tag);
该方法用于通过标签查找一组物体，代码示例如下：
// Instantiates respawnPrefab at the location
// of all game objects tagged "Respawn".
using UnityEngine;
using System.Collections;
public class ExampleClass : MonoBehaviour
{
public GameObject respawnPrefab;
public GameObject[] respawns;
void Start()
{
if (respawns == null)
respawns = GameObject.FindGameObjectsWithTag("Respawn");
foreach (GameObject respawn in respawns)
{
Instantiate(respawnPrefab, respawn.transform.position, respawn.transform.rotation);
}
}
}
FindWithTag：Returns one active GameObject tagged tag. Returns null if no GameObject was found.
语法：public static GameObject FindWithTag(string tag);
该方法为通过标签查找单个物体，但是返回使用指定标签找到的第一个GameObject，如果场景包含多个具有指定标签的GameObjects，则无法保证此方法将返回特定GameObject，注意是非静态的物体，代码演示如下：
using UnityEngine;
using System.Collections;
public class ExampleClass : MonoBehaviour
{
public GameObject respawnPrefab;
public GameObject respawn;
void Start()
{
if (respawn == null)
respawn = GameObject.FindWithTag("Respawn");
Instantiate(respawnPrefab, respawn.transform.position, respawn.transform.rotation);
}
}
后续的官方说明为继承的属性和方法，因为GameObject类继承Object类，在之前已经讨论过，这里不在赘述。
