Switching GameObject[] List if score >= 200? Also does this"[]" mean list or array?

In my project I am trying to make some tiles switch to another [] of tiles if the players score is >=200.(by communicating between 2 scripts) Here's what I'm using to instantiate the tiles and this is working perfectly but now how to change its 2nd set of tiles? I keep getting a null reference error when my score reaches 200.
1/2 Here is the Tile Manager script

Code (CSharp):

1.  
2. public GameObject[] tilePrefabs;//The Default list of gameobjects.
3.  
4.     public GameObject[] increasedDifficultytilePrefabs;//This is the Gameobject[]list I want to switch to.
5.  
6.     private Transform playerTransform;
7.     public AudioClip[] clips;
8.     public AudioSource source;
9.     private float spawnZ = -10.0f;
10.     private float tileLength = 10.0f;
11.  
12.     private int tileAmountOnScreen = 5;
13.     private List<GameObject> activeTiles;
14.  
15.     private float safeZone = 15.0f;
16.  
17.     private int lastPrefabIndex = 0;
18.  
19.     private void Start()
20.     {
21.         activeTiles = new List<GameObject>();
22.         playerTransform = GameObject.FindGameObjectWithTag("Player").transform;
23.  
24.         for (int i = 0; i < tileAmountOnScreen; i++)
25.         {
26.             if (i < 2)
27.                 SpawnTile(0);
28.             else
29.                 SpawnTile();
30.         }
31.     }
32.  
33.     // Update is called once per frame
34.     private void Update()
35.     {
36.         if (playerTransform.position.z - safeZone > (spawnZ - tileAmountOnScreen * tileLength))
37.         {
38.             SpawnTile();
39.             RandomizeSound();
40.             DeleteTile();
41.         }
42.     }
43.  
44.  
45.     public void SpawnTile(int prefabIndex = -1)
46.     {
47.         GameObject go;
48.         if (prefabIndex == -1)
49.             go = Instantiate(tilePrefabs[RandomPrefabIndex()]) as GameObject;
50.         else
51.             go = Instantiate(tilePrefabs[prefabIndex]) as GameObject;
52.         go.transform.SetParent(transform);
53.         go.transform.position = Vector3.forward * spawnZ;
54.         spawnZ += tileLength;
55.         activeTiles.Add(go);
56.  
57.  
58.     }
59.  
60.  
61.     public void SpawnTile2(int prefabIndex = -1)
62.     {
63.         GameObject go;
64.         if (prefabIndex == -1)
65.             go = Instantiate(increasedDifficultytilePrefabs[RandomPrefabIndex()]) as GameObject;
66.         else
67.             go = Instantiate(increasedDifficultytilePrefabs[prefabIndex]) as GameObject;
68.         go.transform.SetParent(transform);
69.         go.transform.position = Vector3.forward * spawnZ;
70.         spawnZ += tileLength;
71.         activeTiles.Add(go);
72.  
73.  
74.     }
75.     void RandomizeSound()
76.     {
77.         source.clip = clips[Random.Range(0, clips.Length)];
78.  
79.     }
80.  
81.  
82.     private void DeleteTile()
83.     {
84.         Destroy(activeTiles[0]);
85.         activeTiles.RemoveAt(0);
86.     }
87.  
88.     private int RandomPrefabIndex()
89.     {
90.         if (tilePrefabs.Length <= 1)
91.             return 0;
92.  
93.         int randomIndex = lastPrefabIndex;
94.         while (randomIndex == lastPrefabIndex)
95.         {
96.             randomIndex = Random.Range(0, tilePrefabs.Length);
97.         }
98.  
99.         lastPrefabIndex = randomIndex;
100.         return randomIndex;
101.     }
102.  
103.  
104.  

1/2 Here is the Level Manager script

Code (CSharp):

1.  
2.  
3. using UnityEngine;
4. using UnityEngine.UI;
5. using UnityEngine.SceneManagement;
6. using System.Collections;
7.  
8. public class LevelManager : MonoBehaviour {
9.     private float score = 0;
10.     public Text ScoreText, StatusText;
11.     //MUSIC
12.  
13.     public AudioSource levelMusic;
14.         public AudioSource gameOverMusic;
15.  
16.     //ForPausingOnDeath / Respawn
17.  
18.     public float waitToRespawn;
19.     public PlayerEngine thePlayer;
20.     public GameObject DeathExplosion;
21.  
22.     //Coins
23.  
24.     public int StartLifeCount;
25.     private int LifeBonusLifeCount;
26.     public int bonusLifeThreshold;
27.     public AudioSource scoreSound;
28.  
29.     //UI
30.     //public Text LifeText;
31.     public Image Life;
32.     public Image Life2;
33.     public Image Life3;
34.  
35.     public Sprite LifeFull;
36.     public Sprite LifeHalf;
37.     public Sprite LifeEmpty;
38.     public int maxHealth;
39.     public int healthCount;
40.  
41.     private bool respawning;
42.  
43.     //Array //[] square brackets mean you want to create an array
44.     public ResetOnRespawn[] objectsToReset;
45.  
46.     public bool invincible;
47.  
48.  
49.     public TileManager Tmanager;
50.     //UI
51.     //public Text livesText;
52.     public int currentLives;
53.     public int startingLives;
54.  
55.     //GameOverScreen
56.     public GameObject gameOverScreen;
57.  
58.  
59.     // Use this for initialization
60.     void Start() {
61.         thePlayer = FindObjectOfType<PlayerEngine>();
62.  
63.         //LifeText.text = "Spires x 9999" + LifeCount;
64.         healthCount = maxHealth;
65.  
66.         objectsToReset = FindObjectsOfType<ResetOnRespawn>();
67.         currentLives = startingLives;
68.         //livesText.text = "Lives x " + currentLives;
69.     }
70.  
71.     // Update is called once per frame
72.     void Update () {
73.         IncreaseScore(1);
74.  
75.         if (score >= 200)
76.         {
77.             Debug.Log("ChangingTileList");
78.             Tmanager.SpawnTile2(int prefabIndex = -1);
79.             //I want to instantiate new array here + CheckPoint Every 500 - 1000 Points?
80.             GameObject tileObj = GameObject.Find("TileManager");
81.             Tmanager = tileObj.GetComponent<TileManager>();
82.  
83.         }
84.  
85.  
86.    
87.         if (healthCount <= 0 && !respawning)
88.         {
89.  
90.             //Respawn();
91.             RestartLevel();
92.             respawning = true;
93.         }
94.  
95.         if(LifeBonusLifeCount >= bonusLifeThreshold)
96.         {
97.             currentLives += 1;
98.             //livesText.text = "Lives x " + currentLives;
99.             LifeBonusLifeCount -= bonusLifeThreshold;
100.  
101.         }
102.  
103.     }
104.  
105.  
106.     public void RestartLevel()
107.     {
108.         StartCoroutine("WaitingDeathScreen");
109.         //SceneManager.LoadScene("InfiniteRunner");
110.  
111.     }
112.  
113.  
114.     public void Respawn()
115.     {//I want my player to restart level if they dont have any lives left
116.         currentLives -= 1;
117.         //livesText.text = "Lives x " + currentLives;
118.         if(currentLives > 0)
119.         {
120.         StartCoroutine("RespawnCo");
121.         } else {
122.             RestartLevel();
123.        
124.             thePlayer.gameObject.SetActive(false);
125.             gameOverScreen.SetActive(true);
126.             levelMusic.Stop();
127.             gameOverMusic.Play();
128.        
129.  
130.  
131.             if (    Input.GetKeyDown(KeyCode.Y))
132.             {
133.  
134.                 SceneManager.LoadScene("0");
135.                 return;
136.             }
137.  
138.             //levelMusic.volume = levelMusic.volume / 2f; //This is if I just want the music to turn itself down when the player dies.
139.         }
140.     }
141.  
142.  
143.     public IEnumerator WaitingDeathScreen()
144.  
145.     {
146.         thePlayer.gameObject.SetActive(false);
147.         gameOverScreen.SetActive(true);
148.         yield return new WaitForSeconds(6);
149.         //gameOverScreen.SetActive(false);
150.         yield return new WaitForSeconds(1);
151.         SceneManager.LoadScene("InfiniteRunner");
152.  
153.     }
154.     public IEnumerator RespawnCo()  //This is a corroutine//
155.     {
156.    
157.  
158.         thePlayer.gameObject.SetActive(false);
159.         Instantiate(DeathExplosion, thePlayer.transform.position, thePlayer.transform.rotation);
160.         yield return new WaitForSeconds(waitToRespawn);
161.  
162.         healthCount = maxHealth;
163.         respawning = false;
164.         UpdateHatMeter();
165.  
166.         StartLifeCount = 0;
167.         //LifeText.text = "Drive:" + LifeCount;
168.         LifeBonusLifeCount = 0;
169.  
170.  
171.         thePlayer.transform.position = thePlayer.respawnPosition;
172.         thePlayer.gameObject.SetActive(true);
173.  
174.         for(int i = 0; i < objectsToReset.Length; i++)
175.         {
176.  
177.        
178.             objectsToReset[i].gameObject.SetActive(true);
179.             objectsToReset[i].ResetObject();
180.         }
181.     }
182.  
183.     public void AddHats(int HatsToAdd)
184.     {
185.         StartLifeCount += HatsToAdd;
186.         LifeBonusLifeCount += HatsToAdd;
187.         //LifeText.text = "Drive:" + LifeCount;
188.         scoreSound.Play();
189.     }
190.  
191.     public void HurtPlayer(int damageToTake)
192.     {
193.         if (!invincible)
194.         {
195.             healthCount -= damageToTake;
196.             UpdateHatMeter();
197.             //thePlayer.Knockback();
198.             //thePlayer.hurtSound.Play();
199.         }
200.     }
201.  
202.     public void GiveHealth(int healthToGive)
203.  
204.     {
205.         healthCount += healthToGive;
206.         if(healthCount > maxHealth)
207.         {
208.  
209.             healthCount = maxHealth;
210.         }
211.         scoreSound.Play();
212.         UpdateHatMeter();
213.  
214.     }
215.  
216.     public void UpdateHatMeter()
217.     {
218.  
219.         switch(healthCount)
220.         {
221.             case 6:
222.                 Life.sprite = LifeFull;
223.                 Life2.sprite = LifeFull;
224.                 Life3.sprite = LifeFull;
225.                 return;
226.  
227.             case 5:
228.                 Life.sprite = LifeFull;
229.                 Life2.sprite = LifeFull;
230.                 Life3.sprite = LifeHalf;
231.                 return;
232.  
233.             case 4:
234.                 Life.sprite = LifeFull;
235.                 Life2.sprite = LifeFull;
236.                 Life3.sprite = LifeEmpty;
237.                 return;
238.  
239.             case 3:
240.                 Life.sprite = LifeFull;
241.                 Life2.sprite = LifeHalf;
242.                 Life3.sprite = LifeEmpty;
243.                 return;
244.  
245.             case 2:
246.                 Life.sprite = LifeFull;
247.                 Life2.sprite = LifeEmpty;
248.                 Life3.sprite = LifeEmpty;
249.                 return;
250.  
251.             case 1:
252.                 Life.sprite = LifeHalf;
253.                 Life2.sprite = LifeEmpty;
254.                 Life3.sprite = LifeEmpty;
255.                 return;
256.  
257.             case 0:
258.                 Life.sprite =  LifeEmpty;
259.                 Life2.sprite = LifeEmpty;
260.                 Life3.sprite = LifeEmpty;
261.                 return;
262.  
263.             default:
264.                 Life.sprite = LifeEmpty;
265.                 Life2.sprite = LifeEmpty;
266.                 Life3.sprite = LifeEmpty;
267.                 return;
268.  
269.         }
270.     }
271.  
272.     public void AddLives(int livesToAdd)
273.     {
274.         scoreSound.Play();
275.         currentLives += livesToAdd;
276.         //livesText.text = "Lives x " + currentLives;
277.  
278.  
279.     }
280.  
281.  
282.  
283.     void Awake()
284.     {
285.         if (instance == null)
286.         {
287.             instance = this;
288.         }
289.         else
290.         {
291.             DestroyImmediate(this);
292.         }
293.     }
294.  
295.     //singleton implementation
296.     private static LevelManager instance;
297.     public static LevelManager Instance
298.     {
299.         get
300.         {
301.             if (instance == null)
302.                 instance = new LevelManager();
303.  
304.             return instance;
305.         }
306.     }
307.  
308.     protected LevelManager()
309.     {
310.  
311.     }
312.  
313.  
314.  
315.     public void ResetScore()
316.     {
317.         score = 0;
318.         UpdateScoreText();
319.     }
320.  
321.     public void SetScore(float value)
322.     {
323.         score = value;
324.         UpdateScoreText();
325.     }
326.  
327.     public void IncreaseScore(float value)
328.     {
329.         score += value;
330.         UpdateScoreText();
331.     }
332.  
333.     private void UpdateScoreText()
334.     {
335.         ScoreText.text = score.ToString();
336.     }
337.  
338.     public void SetStatus(string text)
339.     {
340.         StatusText.text = text;
341.     }
342.  
343.  
344.  
345.  
346.  
347.  
348.  
349.  
350.  
351.  
352.  
353.  
354. }
355.  
356.  
357.  

 

Well, the best advice is to test each part to find what is null.

Plus, you needn't write "int prefabIndex = -1" in spawn tile2. It's already the default, so you can just call SpawnTile2(); and it will be automatic. If you wanted it to be some other number, then you'd write SpawnTile(4);

Now, you have a Tmanager which is public. Did you drag n drop this in the inspector? If so, hopefully that is set properly. There is no need to look for it again the game object, again, then get its component, again.

Hopefully that helps.

 

Oh, sorry forgot to answer the part about [] and whether it's a list or array.
In the declaration, it always means array. However, you can index a list or array with the same syntax, eg:
myListorArray[3] <- 4th spot in array/list (assuming it's at least 4 large )

 

I removed int prefabIndex = -1 and dragged the Tmanager inside the level manager and now it works but I am getting an IndexOutOfRangeException: Array index is out of range and its point to this line within SpawnTile2
go = Instantiate(increasedDifficultytilePrefabs[RandomPrefabIndex()]) as GameObject;

I'm trying to understand why it is out of range hmm

Edit so i added 0 to Tmanager.SpawnTile2(0); and now i have fixed the problem but I do not understand why it works.

Code (CSharp):

1. public void SpawnTile2(int prefabIndex = -1)
2.     {
3.         GameObject go;
4.         if (prefabIndex == -1)
5.             go = Instantiate(increasedDifficultytilePrefabs[RandomPrefabIndex()]) as GameObject; //Here is where the
6. //
7.         else
8.             go = Instantiate(increasedDifficultytilePrefabs[prefabIndex]) as GameObject;
9.         go.transform.SetParent(transform);
10.         go.transform.position = Vector3.forward * spawnZ;
11.         spawnZ += tileLength;
12.         activeTiles.Add(go);
13.  
14.  
15.     }

 

I'm glad it's working (mostly)

Well, when it's -1 (or just default/empty), it takes a random spot from a method.. so that part should work.
If you had code that called that method without any parameter, it would try to index -1 in the list/array, and that is obviously not valid