> For the complete documentation index, see [llms.txt](https://kdoore.gitbook.io/cs2335/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kdoore.gitbook.io/cs2335/project1-code/simple-spawner.md).

# Simple Spawner

### Objects to Spawn - PickUp Prefabs

**PickUp Prefabs** to be Spawned in the MiniGame should have the following configuration:\
 [See PickUp PreFabs](/cs2335/project-1-simple-game/pickup_items.md)

* 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( )`**&#x20;
  * Cancels all Invoked **`SpawnPrefab( )`** methods
  * Sets **activeSpawning** to false;
  * Executes **DestroyAllSpawnedObjects( )**

### **Important Spawner GameObject Configuration Details:** &#x20;

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<br>

![Select Prefab from Assets Tab, Not the Scene Tab](/files/-MHSJm-vdVFBHRfa6fJf)

![Select Prefab From Assets, Not from the Scene](/files/-MHSITQEUy2kb1xwAJ9g)

### Spawner.cs

* The code below creates a simple spawner.&#x20;
* Create a C# Script in your project Assets:  Spawner.&#x20;
* Double-click the script so that it opens in Visual Studio. &#x20;
* Add the code from below to the script.  &#x20;
* In Visual Studio, build to compile the script. &#x20;
* In Unity, Add the **Spawner.cs** component to an empty GameObject, Spawner in the scene.

```java
//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

```