How to activate random gameobjects from a list

Question

I'm a beginner at this and i'm doing horror game where you have to collect coins to win. I spread 33 coins around the map in different locations and I want to activate only 8 of them chosen randomly at start so they aren't always in the same spots. And when the game ends and start over the coins are again in random spots. So if you have a solution to my problem please help :)

Answer 1

Best Answer

Answer by callen · Jan 24, 2018 at 08:35 PM

bhavinbhai2707 was on the right track, but here is the bug-free version.

 // You need to have an array of all your coins. you could do it with a public variable, and drag them into the inspector...
 public GameObject[] coins;
 
 void Start() {
     // ...or, you could also less-efficiently get the coins here with something like:
     // var coins = FindObjectsOfType<Coin>();
 
     for(int i=0; i<8; i++)
     {
         int rnd = Random.Range(0, coins.Length);
         if(!coins[rnd].activeSelf) coins[rnd].SetActive(true);
         else i--; // repeat loop iteration to try and find a disabled coin
     }
 }

The main issue with the other answer is that it cannot guarantee you will always activate 8 coins. You could, in a rare case, activate just 1, or any number from 1 to 8. My version should work, assuming you have more than 8 coins in the array (otherwise it will infinite loop!)

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Answer 2

Answer by bhavinbhai2707 · Jan 24, 2018 at 08:23 PM

one of the way is to spread coins and place them manually around map(deactivated manually by default) and store them in array and activate randomly

  public GameObject[] coins;         //array of coins from scene view
 
    private void Start()
   {
       spawnRandom();
   }
     private void spawnRandom()
     {
         int last = 0;                   
         for (int i = 0; i < 8; i++)    //i < 8 since u want 8 coins
         {
             int num = Random.Range(0, 20);           //Random.Range fuction throws random number
             while (num == last)                         //checking if new number is not equal to last number
                 num = Random.Range(0, 20);          //if yes then reassign num so the same coin wont reactivate
             coins[num].SetActive(true)
             last = num;
         }
     }

second way is you can spawn prefab of coin Randomly around map

 public GameObject coinprefab;         //array of coins from scene view
     private float xlimit, zlimit;         //basically the limit of the boundary
 
 private void Start()
 {
      spawnRandom();
 }
     private void spawnRandom()
     {
        for(int i = 0; i < 8; i++)
         {
             xlimit = Random.Range(-xlimit, xlimit);            //random x position
             zlimit = Random.Range(-zlimit, zlimit);            //random z position 
            Instantiate(coinprefab, new Vector3(xlimit, 3f, zlimit), Quaternion.identity);         //spawning the coin in scene & set y of vector3 according to your need
         }
     }

These codes are untested. I hope these helps :)

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callen · Jan 24, 2018 at 09:12 PM 0

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The second answer would not work unless the map was empty - otherwise coins will spawn inside of walls or other inaccessible places. Also the OP said he already placed his coins on the map, presumably in places that will be more fun than completely-random ones would.

So, The first answer is better conceptually, but you need to fix the following issues:

OP said there were 33 coins, but you only do Random.Range(0, 20) which will make the last 13 coins unusable. You should just instead do Random.Range(0, coins.Length);
You are trying to use "last" to prevent the same coin from being chosen multiple times, but what you coded doesn't do that. For example, your first Random returns 9, and last is 9, so you call Random.Range again... but what if you get a 9 again? Your code doesn't handle this. The same can be said for the case where you get 9, then on next loop you get 5, then on next loop you get 9 again - at this point last==5, so it will not detect the duplicate.
gameObject.SetActive(coins[num]) is incorrect, should be coins[num].SetActive(true)

Take note of my answer, as it solves all of these issues with just a few lines of code.

bhavinbhai2707 callen · Jan 24, 2018 at 09:29 PM 0

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thanx for correcting mate :), i knew there are some bugs and as i wrote the code itself on this websites editor. i will take note of all the issue thanx :)

Answer 3

Answer by yoda8789 · Jan 24, 2018 at 09:38 PM

Thanks to both of you! Couldnt have done that without your help :) @bhavinbhai2707 @callen

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How to activate random gameobjects from a list

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