unity-atoms/Assets/UnityAtoms/GameFunctions/GetUnusedGameObject/GetUnusedGameObject.cs

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

namespace UnityAtoms
{
    /* Gets an unused GameObject from the GameObjectList. If an GameObject is used or not is determined by IsUsed GameFunction.
	 * If no unused GameObject is found a new one is instantiated and added to the GameObjectList.
	 */
    [CreateAssetMenu(menuName = "UnityAtoms/Game Functions/Get Unused GameObject")]
    public class GetUnusedGameObject : GameObjectVector3QuaternionFunction
    {
        [SerializeField]
        private GameObjectList List;

        [SerializeField]
        private GameObject Prefab;

        [SerializeField]
        private BoolGameObjectFunction IsUsed;

        public override GameObject Call(Vector3 position, Quaternion quaternion)
        {
            if (IsUsed == null)
            {
                Debug.LogWarning("IsUsed must be defined!");
            }

            for (int i = 0; i < List.Count; ++i)
            {
                if (!IsUsed.Call(List[i]))
                {
                    List[i].transform.position = position;
                    List[i].transform.rotation = quaternion;
                    return List[i];
                }
            }

            var newGameObject = Instantiate(Prefab, position, quaternion);
            List.Add(newGameObject);
            return newGameObject;
        }
    }
}