# 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( )`**
* 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
### 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.
```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();
foreach (PickUp item in items)
{
Destroy(item.gameObject);
}
}
}// end class Spawner
```
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