Spawning Objects in Unity without the Clutter

by Lance Gold

Take a look at the two classes of a game.


public class Enemy : MonoBehaviour
{
...
   if (transform.position.y < _bottomEdge)
   {
      _horizontalRandom = UnityEngine.Random.Range(_leftEdge, _rightEdge);
      transform.position = new Vector3(_horizontalRandom, _topEdge, 0);
   }
}

This class Enemy repositions a falling object at the top after it reaches the bottom.

The second class SpawnManager adds a new object every five seconds.


public class SpawnManager : MonoBehaviour
{
...
    IEnumerator SpawnRoutine()
    {
        while (true)
        {
            _horizontalRandom = UnityEngine.Random.Range(_leftEdge, _rightEdge);
            transform.position = new Vector3(_horizontalRandom, _topEdge, 0);
            Instantiate(_enemyPrefab, transform.position, Quaternion.identity);
    
            yield return new WaitForSeconds(5.0f);
        }
    }
}

Running together, there will be more and more falling Enemy objects.

Too many objects

Childed (pronouced child•ed)

From the training:

We can organize these enemies to be instantiated, but then be childed inside of the spawn manager within an enemy container.

(a) Instantiate the object

(b) Get a reference to the object

(c) Assign the parent of the object to, for example, the SpawnManager or whatever the container is.

First define a container for the Enemy objects, an Empty Object with Spawn_Manager as the parent.

Create Empty object under Spawn_Manager

The Enemy Container object will be a place where we can place all our Enemy objects inside of.

Enemy Container object Hierarchy

Code a matching GameObject in the .cs file to work with.


public class SpawnManager : MonoBehaviour
{
    [SerializeField]
    private GameObject _enemyPrefab;
    [SerializeField]
    private GameObject _enemyContainer;
...
}



Save and view how added variable appears in Inspector for Spawn_Manager:





Enemy Container variable in the Spawn_Manager Inspector





Highlight the Spawn_Manager, drag and drop the Enemy Container for coding access.



A Brief Review of Variables


Here are a C# message and a GameObject. Both not accessible:



Debug.Log("5");

Instantiate(_enemyPrefab, transform.position, Quaternion.identity);




Better and accessible when assigned to a variable:



public class SpawnManager : MonoBehaviour
...
   [SerializeField]
   private GameObject _enemyContainer;

   IEnumerator SpawnRoutine(float waitTime)
    {
        while (true)
        {   
            Vector3 posToSpawn = new Vector3(Random.Range(_leftEdge, _rightEdge), _topEdge, 0);
            GameObject newEnemy = Instantiate(_enemyPrefab, posToSpawn, Quaternion.identity);
            newEnemy.transform.parent = _enemyContainer.transform;
    ...
        }
    }
}





newEnemy is type “GameObject”

something.transform.parent is type “transform”

_enemyContainer is type “GameObject”

_enemyContainer.transform is type “transform”



Before save and run:


… spawned Enemy objects not inside “Enemy Container” in Hierarchy





Spawning outside of new “Enemy Container”




After save and run:


… spawned Enemy object now inside “Enemy Container” in Hierarchy.





Spawning inside new “Enemy Container”