Simple Spawner

Script Component to spawn PickUp Prefab gameObjects.

Objects to Spawn - PickUp Prefabs

PickUp Prefabs to be Spawned in the MiniGame should have the following configuration: See PickUp PreFabs

• PickUp GameObjects should be a PreFab

• A SpriteRenderer Component

• At least 1 Collider2D component with IsTrigger set to true (can have additional nested Collider2D components if necessary)

• A PickUp script component, with the public attributes like: value, type set in the inspector.

• GameObject: Tag: "Collectible" or "Hazard"

• Can have a Rigidbody2D if the spawned object will be moving

• Can have an Animator component if the object will be animated

  Important: The PickUp Prefabs must have Tag that corresponds to Tags in OnTriggerEnter2D( ).

Simple Spawner Logic

Logic Overview: Define variables that can be customized for each instance of a Spawner:

• Specify PickUp prefabs to spawn ( good, bad )

• Specify total number of prefabs to spawn (numToSpawn)

• Specify probability of bad prefabs to spawn. (chanceToSpawnBad)

• Constrain where objects will be spawned. (xRange, yRange)

• Determine time between spawning objects (pauseTime)

• Define boolean variable that can toggle: (stop, start) spawning

Spawner Methods, Helper Methods

Start Spawning:

• SpawnPrefab( )

  • private method, executed in a loop in StartSpawning( )

  • spawns 1 prefab instance - with some probability of it being good / bad type

  • will only spawn a prefab if activeSpawning is true;

• StartSpawning ( )

  • public method to be executed in MiniGameManager

  • For testing, we'll start with calling this in Start( ) - we'll remove this code later

  • has a loop that invokes SpawnPrefab( ) multiple times with delays

Stop Spawning:

• DestroyAllSpawnedObjects( )

  • Creates Array of PickUps by Finding all items of type < PickUp > in the scene

• StopAllSpawning( )

  • Cancels all Invoked SpawnPrefab( ) methods

  • Sets activeSpawning to false;

  • Executes DestroyAllSpawnedObjects( )

Important Spawner GameObject Configuration Details:

When initializing the Inspector Panel for Spawner Component: 1. Delete all PickUp Prefab gameObjects from the Scene 2. Select Original Prefab from Assets: GoodPrefab, BadPrefab (from the Assets tab) see image below

Select Prefab from Assets Tab, Not the Scene Tab

Select Prefab From Assets, Not from the Scene

Spawner.cs

• The code below creates a simple spawner.

• Create a C# Script in your project Assets: Spawner.

• Double-click the script so that it opens in Visual Studio.

• Add the code from below to the script.

• In Visual Studio, build to compile the script.

• In Unity, Add the Spawner.cs component to an empty GameObject, Spawner in the scene.

//Sept 17, 2020
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Spawner : MonoBehaviour
{
    [Header("Set in Inspector")]
    public GameObject goodPrefab, badPrefab;

    public bool activeSpawning = false;

    [SerializeField]
    int pauseTime = 2; //may need to customize for your game

    [SerializeField]
    int numToSpawn = 10; //customize as needed

    [SerializeField]
    float chanceToSpawnBad = 0.10f; //modify as needed

    [SerializeField]
    float xRangeLeft = -8.0f; //customize as needed

    [SerializeField]
    float xRangeRight = 8.0f; //customize as needed

    [SerializeField]
    float yRangeTop = -2.0f; //customize as needed

    [SerializeField]
    float yRangeBottom = -3.5f; //customize as needed

    // Start is called before the first frame update
    void Start()
    {
        activeSpawning = true; //remove this code later
        StartSpawning(); //remove this code later, move to MiniGameManager
    }


    ///Will be exectued in MiniGameManager when startButton clicked
    //MiniGameState is set to active
    public void StartSpawning()
    {
        Debug.Log("Start Spawning called");
        //Loop generates multiple delayed invocations of SpawnPrefab( ) method.
        for (int i = 0; i < numToSpawn; i++)
        {
            Invoke("SpawnPrefab", pauseTime * i * 2);  //Delays between SpawnPrefab( ) exection
        }
    }

    //Executed from the StartSpawning method
    //Many instances of this method will be invoked 
    void SpawnPrefab()
    {
        if (activeSpawning) //won't actually spawn anything unless this is true 
        {
            //Where to spawn based on transform of Spawner gameObject

            Vector3 position = transform.localPosition;
            position.x = Random.Range(xRangeLeft, xRangeRight);
            position.y = Random.Range(yRangeBottom, yRangeTop);

            float rand = Random.value;
            GameObject prefab; //temp variable 
            if (rand < chanceToSpawnBad)
            { //spawn bad prefab
                prefab = Instantiate(badPrefab, position, transform.rotation);
            }
            else  //instantiate good one
            {
                prefab = Instantiate(goodPrefab, position, transform.rotation);
            }
            prefab.transform.SetParent(this.transform); //all spawned objects will be children of the Spawner gameObject
        }
    }//end SpawnPrefab

    //This will be executed from MiniGameManager
    public void StopAllSpawning()
    {
        CancelInvoke("SpawnPrefab");  //cancels all SpawnPrefab( ) methods waiting to be executed
        activeSpawning = false;
        DestroySpawnedObjects();
    }

    //Exectued in StopAllSpawning
    private void DestroySpawnedObjects()
    {
        PickUp[] items = FindObjectsOfType<PickUp>();
        foreach (PickUp item in items)
        {
            Destroy(item.gameObject);
        }
    }

}// end class Spawner