Unity GetComponentについて

Question

こんにちは。いつもありがとうございます。
Unity、C#ともに初心者でわからないので質問させてください。

#あるScriptから他のScript内のオブジェクトを削除するには

GetComponent<TexturePainter> ();でアクセスできると思っていたのですが、ある時はNullを、またある時はGetComponentを使ったところから下のコードが実行されません。

１つ目のコードが適応されている3dオブジェクトをクリックすると２つ目のコード内のbrushContainer内の子要素を削除したいのですが、どうすれば良いのでしょうか？？

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

public class EraseCanvas : MonoBehaviour {
	//int brushCounter=0,MAX_BRUSH_COUNT=1000; //To avoid having millions of brushes
	public Material baseMaterial; // The material of our base texture (Were we will save the painted texture)
	public GameObject bContainer; //The cursor that overlaps the model and our container for the brushes painted
//	// Use this for initialization
//	void Start () {
//		
//	}
	
	// Update is called once per frame
	void Update(){
//		Debug.Log (brushContainer);
//		Debug.Log (GetComponent<TexturePainter> ());
//		Debug.Log (brushContainer);
		if(Input.GetMouseButtonDown(0)){
			Transform cam = Camera.main.transform;
			var ray = new Ray(cam.position, cam.forward);
			RaycastHit hit;
			if(Physics.Raycast (ray, out hit)){
				var e = hit.transform.GetComponent<EraseCanvas> ();
				if (e != null) {
					Debug.Log ("|----------------------------------");
					Debug.Log (bContainer.GetComponent<TexturePainter>().brushContainer);
					Debug.Log ("----------------------------------|");
					foreach (Transform child in bContainer.GetComponent<TexturePainter> ().brushContainer.transform) {//Clear brushes
						Destroy(child.gameObject);
						Debug.Log ("hi again");
					}
				}
			}
		}
	}



	void ClearCanvas(){
		//brushCounter=0;
		//System.DateTime date = System.DateTime.Now;
//		//RenderTexture.active = canvasTexture;
//		Texture2D tex = new Texture2D(canvasTexture.width, canvasTexture.height, TextureFormat.RGB24, false);		
//		tex.ReadPixels (new Rect (0, 0, canvasTexture.width, canvasTexture.height), 0, 0);
//		tex.Apply ();
		//RenderTexture.active = null;
		//baseMaterial.mainTexture =tex;	//Put the painted texture as the base

		//StartCoroutine ("SaveTextureToFile"); //Do you want to save the texture? This is your method!
//		Invoke ("ShowCursor", 0.1f);
	}
		
}

２.呼び出そうとしているオブジェクトがあるコード

/// <summary>
/// CodeArtist.mx 2015
/// This is the main class of the project, its in charge of raycasting to a model and place brush prefabs infront of the canvas camera.
/// If you are interested in saving the painted texture you can use the method at the end and should save it to a file.
/// </summary>


using UnityEngine;
using UnityEngine.UI;
using System.Collections;


public enum Painter_BrushMode{PAINT,DECAL};
public class TexturePainter : MonoBehaviour {
	public GameObject brushCursor,brushContainer; //The cursor that overlaps the model and our container for the brushes painted
	public Camera sceneCamera,canvasCam;  //The camera that looks at the model, and the camera that looks at the canvas.
	public Sprite cursorPaint,cursorDecal; // Cursor for the differen functions 
	public RenderTexture canvasTexture; // Render Texture that looks at our Base Texture and the painted brushes
	public Material baseMaterial; // The material of our base texture (Were we will save the painted texture)

	Painter_BrushMode mode; //Our painter mode (Paint brushes or decals)
	float brushSize=1.0f; //The size of our brush
	public Color brushColor; //The selected color
	int brushCounter=0,MAX_BRUSH_COUNT=1000; //To avoid having millions of brushes
	bool saving=false; //Flag to check if we are saving the texture

	
	void Update () {
		//brushColor = ColorSelector.GetColor ();	//Updates our painted color with the selected color
		// brushColor = customBrushColor; // This is the brush color
		if (Input.GetMouseButton(0)) {
			DoAction();
		}
		UpdateBrushCursor ();
	}

	//The main action, instantiates a brush or decal entity at the clicked position on the UV map
	void DoAction(){	
		if (saving)
			return;
		Vector3 uvWorldPosition=Vector3.zero;		
		if(HitTestUVPosition(ref uvWorldPosition)){
			GameObject brushObj;
			if(mode==Painter_BrushMode.PAINT){

				brushObj=(GameObject)Instantiate(Resources.Load("TexturePainter-Instances/BrushEntity")); //Paint a brush
				brushObj.GetComponent<SpriteRenderer>().color=brushColor; //Set the brush color
			}
			else{
				brushObj=(GameObject)Instantiate(Resources.Load("TexturePainter-Instances/DecalEntity")); //Paint a decal
			}
			brushColor.a=brushSize*2.0f; // Brushes have alpha to have a merging effect when painted over.
			brushObj.transform.parent=brushContainer.transform; //Add the brush to our container to be wiped later
			brushObj.transform.localPosition=uvWorldPosition; //The position of the brush (in the UVMap)
			brushObj.transform.localScale=Vector3.one*brushSize;//The size of the brush
		}
		brushCounter++; //Add to the max brushes
		if (brushCounter >= MAX_BRUSH_COUNT) { //If we reach the max brushes available, flatten the texture and clear the brushes
			brushCursor.SetActive (false);
			saving=true;
			Invoke("SaveTexture",0.1f);
			
		}
	}
	//To update at realtime the painting cursor on the mesh
	void UpdateBrushCursor(){
		Vector3 uvWorldPosition=Vector3.zero;
		if (HitTestUVPosition (ref uvWorldPosition) && !saving) {
			brushCursor.SetActive(true);
			brushCursor.transform.position =uvWorldPosition+brushContainer.transform.position;									
		} else {
			brushCursor.SetActive(false);
		}		
	}
	//Returns the position on the texuremap according to a hit in the mesh collider
	bool HitTestUVPosition(ref Vector3 uvWorldPosition){
		RaycastHit hit;
		// Vector3 cursorPos = new Vector3 (Input.mousePosition.x, Input.mousePosition.y, 0.0f);

		Vector3 cursorPos = new Vector3 (Screen.width/2, Screen.height/2, 0.0f);

		//Debug.Log("Screen.width/2 " + Screen.width/2);
		//Debug.Log("0.5f " + 0.5f);

		Ray cursorRay = sceneCamera.ScreenPointToRay (cursorPos);
		
		if (Physics.Raycast(cursorRay,out hit,200)){
			MeshCollider meshCollider = hit.collider as MeshCollider;
			
			var e = hit.transform.GetComponent<canvasScript> ();

			if (meshCollider == null || meshCollider.sharedMesh == null){
				return false;			
			}else if(e != null){
				Vector2 pixelUV  = new Vector2(hit.textureCoord.x,hit.textureCoord.y);
				uvWorldPosition.x=pixelUV.x-canvasCam.orthographicSize;//To center the UV on X
				uvWorldPosition.y=pixelUV.y-canvasCam.orthographicSize;//To center the UV on Y
				uvWorldPosition.z=0.0f;
				return true;
			}
		}
		else{		
			return false;
		}
		return false;
		
	}



	//Sets the base material with a our canvas texture, then removes all our brushes
	void SaveTexture(){		
		brushCounter=0;
		System.DateTime date = System.DateTime.Now;
		RenderTexture.active = canvasTexture;
		Texture2D tex = new Texture2D(canvasTexture.width, canvasTexture.height, TextureFormat.RGB24, false);		
		tex.ReadPixels (new Rect (0, 0, canvasTexture.width, canvasTexture.height), 0, 0);
		tex.Apply ();
		RenderTexture.active = null;
		baseMaterial.mainTexture =tex;	//Put the painted texture as the base
		foreach (Transform child in brushContainer.transform) {//Clear brushes
			Destroy(child.gameObject);
		}
		//StartCoroutine ("SaveTextureToFile"); //Do you want to save the texture? This is your method!
		Invoke ("ShowCursor", 0.1f);
	}
	//Show again the user cursor (To avoid saving it to the texture)
	void ShowCursor(){	
		saving = false;
	}

	////////////////// PUBLIC METHODS //////////////////

	public void SetBrushMode(Painter_BrushMode brushMode){ //Sets if we are painting or placing decals
		mode = brushMode;
		brushCursor.GetComponent<SpriteRenderer> ().sprite = brushMode == Painter_BrushMode.PAINT ? cursorPaint : cursorDecal;
	}
	public void SetBrushSize(float newBrushSize){ //Sets the size of the cursor brush or decal
		brushSize = newBrushSize;
		brushCursor.transform.localScale = Vector3.one * brushSize;
	}

	////////////////// OPTIONAL METHODS //////////////////

	#if !UNITY_WEBPLAYER 
		IEnumerator SaveTextureToFile(Texture2D savedTexture){		
			brushCounter=0;
			string fullPath=System.IO.Directory.GetCurrentDirectory()+"\\UserCanvas\\";
			System.DateTime date = System.DateTime.Now;
			string fileName = "CanvasTexture.png";
			if (!System.IO.Directory.Exists(fullPath))		
				System.IO.Directory.CreateDirectory(fullPath);
			var bytes = savedTexture.EncodeToPNG();
			System.IO.File.WriteAllBytes(fullPath+fileName, bytes);
			Debug.Log ("<color=orange>Saved Successfully!</color>"+fullPath+fileName);
			yield return null;
		}
	#endif
}

わかる方おられましたら、ご教授願います。よろしくお願いします。

Answer 1

「クリックしたオブジェクトに付いているEraseCanvas」が対象であるなら、
foreach (Transform child in bContainer.GetComponent<TexturePainter> ().brushContainer.transform) {
の部分は、bContainerの前にe.を入れた
foreach (Transform child in e.bContainer.GetComponent<TexturePainter> ().brushContainer.transform) {
になります。
（eが無いと「自分自身のbContainer」を対象にしようとします）

ちなみにここを直しても、以下の条件下でエラーが発生します。

• bContainerがnullの時
• bContainerにTexturePainterが付いていない時
• bContainerのTexturePainterのbrushContainerがnullの時

これはUnityの仕様です。
なので適宜nullチェックを挟むか、絶対にnullが発生しないような構造とする
（スクリプト上で確実に変数にオブジェクトを入れる等）必要があるかと思います。