Having some trouble with arrays, not sure why.

I've written a little script that's meant to randomize a star's color. I'm using 3 arrays, with colors set in the inspector, and a random rarity value to choose which array to pick from.

Code (CSharp):

1.     public Color[] commonColors;
2.     public Color[] rareColors;
3.     public Color[] ultraRareColors;
4.     int rarity;
5.     Color chosenColor;
6.     int index;
7.  
8.     void Start ()
9.     {
10.         rarity = Random.Range(0,20);
11.  
12.         if(rarity > 5)
13.         {
14.             index = Random.Range(0, commonColors.Length);
15.             chosenColor = commonColors[index];
16.         }
17.         else if(rarity > 2)  
18.         {
19.             index = Random.Range(0, rareColors.Length);
20.             chosenColor = rareColors[index];
21.         }
22.         else
23.         {
24.             index = Random.Range(0, ultraRareColors.Length);
25.             chosenColor = ultraRareColors[index];
26.         }
27.  
28.         particleSystem.startColor = chosenColor;
29.     }

Honestly, it works perfectly, my only concern however, is the errors it spits out in the console saying "IndexOutOfRangeException: Array index is out of range".

I'm not really sure why this is happening; as far as I've seen searching around, I shouldn't be having any problems. I thought maybe using the array.length was setting the index outside of the array's actual length, and tried subtracting 1 from it, but that just made it not choose the last color in the array, and it still gave the error. Anyone here see what I've done wrong?

 

Error message tells you which line it's happening on. Which is it ? - I don't immediatly see anything wrong with the posted code

 

The array index is zero-based. Try *.Length - 1, otherwise you're reading one step past the end.

 

This advice is incorrect.
The code as posted seems correct to me.

Does it fail consistently ?
Where does it fail ?

Perhaps you could add some Debug.Log() statements to print the index and array.Length values to assist resolving this issue.

//---
Just to satisfy my curiosity,
are these variables used elsewhere in the class than in the Start method.

Code (CSharp):

1.     int rarity;
2.     Color chosenColor;
3.     int index;

They could be local scope ( defined inside ) the Start method if not used elsewhere.

 

It's not consistent, no. It seems like only a quarter of the objects in the scene give the error, but they all occur on the lines where I set the chosen color. Also, the code in my post is the entire script for now, but I'll be using the rarity value later to define some other things. I'll put the other two into the start function though, and I'll try the debug.log idea and report back.

 

Alright, so I gave it a shot adding Debug.Logs for the array lengths and also the index used, and as far as I can tell, there's absolutely no pattern to the errors, and all of the indexes are within the length of the array.

I guess I can just get away with ignoring it for now; it doesn't seem to be affecting anything really, it's just clogging up the console.

 

Array.Length is NOT 0 based, this means that if you call it on an Array with say 5 elements in it, it returns 5, while the maximum index is 4 (arrays are 0-based). Random.Range(min, max) is Inclusive, that means that the min and max value can be included. This means, that if you set index as Random.Range(0, Array.Length) the maximum selected value can be 5. However ,Array[5] would be out of range, and that is the issue you run in at the moment. What orb said is correct.

sources:
http://docs.unity3d.com/ScriptReference/Array.html
http://docs.unity3d.com/ScriptReference/Random.Range.html

 

Timelog,
Sorry, you are both misunderstanding Random.Range()
read the documentation again.

public static function Range(min: float, max: float): float;
Returns a random float number between and min [inclusive] and max [inclusive] (Read Only).

public static function Range(min: int, max: int): int;
Returns a random integer number between min [inclusive] and max [exclusive] (Read Only).
If max equals min, min will be returned. The returned value will never be max unless min equals max.

 

Your code looks good, best guess is that you may not have added color values to some arrays on the GameObjects that are throwing errors. So check to insure that each array on each GameObject has at least 1 color value. If you color arrays/values are going to be the same for all GameObjects you may want to define them in code.

 

I ran into the same issue recently never 100% locked down why it was happening but you can do this to stop the errors:

Code (CSharp):

1.  
2.     index = [URL='http://unity3d.com/support/documentation/ScriptReference/30_search.html?q=Random']Random[/URL].[URL='http://unity3d.com/support/documentation/ScriptReference/30_search.html?q=Range']Range[/URL](0, commonColors.[URL='http://unity3d.com/support/documentation/ScriptReference/30_search.html?q=Length']Length[/URL]);
3.  
4.     if(index >= commonColors.length){
5.         index = commonColors.length-1;
6.     }
7.  
8.     chosenColor = commonColors[index];
9.  

You are more correcting the problem after that fact but it will stop the errors for now

 

Woops, completely missed that part way to late over here to concentrate It seems that in that case, the Random.Range does return a float value for whatever reason while it really shouldn't, and indeed, the code looks correct :/

 

Hmm, interestingly enough, I copied my code over into a different script, and it seems to have completely stopped the error messages. Must have been some little glitch somewhere behind the scenes. Sorry to waste everyone's time; I'm fairly new to Unity, and I figured it had to be my fault somehow, heh.

On the bright side though, I've learned a ton about how arrays work, so thanks for that!

 

Regarding the comment by ReeVee

Something like this may help.

Code (CSharp):

1.     public Color[] commonColors = new Color[] {
2.                                                   Color.blue,
3.                                                   Color.yellow,
4.                                                   Color.magenta,
5.                                                   Color.black,
6.                                                   Color.white
7.                                               };
8.  
9.     public Color[] rareColors = new Color[] {
10.                                                 Color.red,
11.                                                 Color.gray,
12.                                                 Color.cyan,
13.                                                 new Color32(128, 255, 128, 255)
14.                                             };
15.  
16.     public Color[] ultraRareColors = new Color[] {
17.                                                      Color.green,
18.                                                      Color.cyan
19.                                                  };
20.  
21.     private int rarity;
22. //< .. >