毎日出題の３日目第三問の答え

CreatePrimitiveByMouse2.cs

public class CreatePrimitiveByMouse2 : MonoBehaviour {
	GameObject primitive = null;
	int currentPrimitiveIndex = 0;
	List<PrimitiveType> primitiveTypeList = new List<PrimitiveType>();
	void Start()
	{
		// 必要なPrimitiveTypeを用意
		this.primitiveTypeList = new List<PrimitiveType>()
		{
			PrimitiveType.Sphere,
			PrimitiveType.Capsule,
	        PrimitiveType.Cylinder,
			PrimitiveType.Cube
		};
	}
	void Update () {
		if (Input.GetMouseButton(0))
		{
			var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
			RaycastHit hit;
			if (Physics.Raycast(ray, out hit, float.MaxValue))
			{
				// Nullなら新規作成。
				if( this.primitive == null )
					this.primitive = this.CreatePrimitive(hit.point);
				// nullでないなら追従
				else
					this.primitive.transform.position = hit.point;

			}
		}
		else if (Input.GetMouseButtonUp(0))
		{
			// ボタンを話したら消滅
			if (this.primitive != null)
			{
				Destroy(this.primitive);
			}
		}
	}

	// 仕様にあったインターフェースで対象おオブジェクトを循環させる
	GameObject CreatePrimitive(Vector3 position)
	{
		if (this.currentPrimitiveIndex >= this.primitiveTypeList.Count  )
		{
			this.currentPrimitiveIndex = 0;
		}
		var p = GameObject.CreatePrimitive( primitiveTypeList[this.currentPrimitiveIndex ++ ] );
		Destroy(p.GetComponent<Collider>());
		p.transform.position = position;
		return p;
	}
}