Spawning random object at predefined locations

Questions & Answers
1

Hello,

I searched around and found different pieces of code that even though separately cover all parts of my problem, when put together are not working…

Here is what I need to do :

  1. I have 14 spawn points located on my terrain.
  2. I have 14 game objects to spawn.
  3. What I need is to spawn one object (chosen at random, let’s say Number3 from gameobject list) at spawn point Nr1 (spawn points can be iterated based on their number)
  4. Next iteration is to choose again a new object from the updated gameobject list(the gameobject list, minus Number3 which was previously spawned) and spawn it at spawn point Nr2
  5. Iterations continue until all objects are uniquely spawned on all the spawn points.

I need this for my game world map, where the objects will represent loading triggers for the respective scenes.

Help is very much appreciated as I am still a newbie in scripting.
Thank you.

2

One way to do it is to shuffle the spawn point array, then you can do something like this:

for( int i = 0; i < spawnPoints.length; ++i ) {
   /*Spawn gameObjectArray <em>at spawnPoints_;*/_</em>

}
To do a shuffle, you can go for a [Fisher–Yates shuffle][1]:
Transform [] myArray = …;

int i = myArray.length;

while( --i >= 0 ) {
int randIndex = Random.Range( 0, myArray.length );

//Swap i with a random index
Transform temp = myArray*;*
myArray = myArray[randIndex];
myArray[randIndex] = temp;
}
----------
If you are using a collection to store the spawn points, then you can go for this:
List spawnPoints = …;

//You can use either collections or array to store the spawned object, it doesn’t matter
GameObject[] spawnThis = …;

…

for( int i = 0; i < spawnThis.Length; ++i ) {
int randIndex = Random.Range( 0, spawnPoints.Count );
Transform sp = spawnPoints[randIndex];
spawnPoints.RemoveAt( randIndex );

/Spawn spawnThis _at sp/
}_

[1]: Fisher–Yates shuffle - Wikipedia

3

for( int i = 0; i < spawnThis.Length; ++i )
{
Debug.Log (sizeOfList);
int randIndex = Random.Range( 0, sizeOfList );
Transform sp = spawnPoints[randIndex];
spawnPoints.RemoveAt( randIndex );
}

You are changing the values inside your list during the loop, so that your sizeOfList != spawnPoints.Count. If your Random,Range then tries to get the spawnPoint from 0 to sizeOfList it may get an index of your list no longer existing ( sizeOfList == 14, spawnPoints.Count == 13 ) which ends up in a null reference exception.
You should not Remove the spawnPoint inside the loop OR you should simply reduce your sizeOfList after RemoveAt by 1 as well.

Greetz