Unity 4 C# - IndexOutOfRangeException: Array index is out of range

Question

Apologies if this is answered somewhere else but I believe my problem is very specific and I haven't got the slightest clue, based on past experience in python, why this code returns the error:

IndexOutOfRangeException: Array index is out of range.
(wrapper stelemref) object:stelemref (object,intptr,object)
MissionGen.Start () (at Assets/Scripts/MissionGen.cs:59)

I am currently in the process of learning C# in the Unity engine, and have created a small class experimentation script designed to generate missions using OOP, selecting target names from an array - but obviously, I have no idea why this won't work. As I believe the equivalent error in python only occurs when I have tried to refrence an array element that doesn't exist. And though this is probably also the case here, due to the way the code is written, I don't understand why. Anyway, here is the full script!:

// Simple mission generation script, using arrays and object orientated programming. Designed to be
//  upgraded at a later date. 

using UnityEngine;
using System.Collections;

// Mission generation template

public class MissionGen : MonoBehaviour {

    public string[] t_list_t = new string[] {"Dave", "Johnson", "Hadaki", "Tim", "Timothy", "Chris Roberts"};
    public string[] t_list_c_col = new string[] {"Blue", "Yellow", "Green", "Black", "Orange", "Purple"};
    public string[] t_list_h_col = new string[] {"Black", "Green", "Orange", "Blue", "Red", "Brown"};

    public class MissionTemplate {

    // Mission properties

        public int id;
        public string t_name;
        public string t_coat;
        public string t_hat;
        public string type;
        public int reward1;
        public string reward2;

    // A method, for displaying the attributes of an individual mission.

    public void ShowMission () {
        print ("MISSION ID: " + id);
        print ("TARGET NAME: " + t_name);
        print ("TARGET COAT COLOUR: " + t_coat);
        print ("TARGET HAT COLOUR: " + t_hat);
        print ("MISSION TYPE: " + type);
        print ("REWARD 1 (Money): " + reward1);
        print ("REWARD 2 (Item): " + reward2);
    }
}

// Mission array generation. Change the array range to generate more missions for use in the game.

    void Start() {

        // Change this variable to decide how many missions to generate:

        int gen = 50;

        // Change the above variable to designate the number of missions to generate.

        MissionTemplate[] MISSION = new MissionTemplate[gen];

        for (int i = 1; i <= gen; i++)
        {   

        int t_pick = Random.Range (0,5);
        int t_coat_col = Random.Range (0,5);
        int t_hat_col = Random.Range (0,5);

        MISSION[i] = new MissionTemplate();

        MISSION[i].id = i;
        MISSION[i].t_name = t_list_t[t_pick];
        MISSION[i].t_coat = t_list_c_col[t_coat_col];
        MISSION[i].t_hat = t_list_h_col[t_hat_col];
        MISSION[i].type = "Assassination";
        MISSION[i].reward1 = 0;
        MISSION[i].reward2 = "";
        }

        for (int i = 1; i <= gen; i++)
        {
        MISSION[i].ShowMission();   
        }
    }
}

As a breakdown, I believe the problems arise between the following code:

    for (int i = 1; i <= gen; i++)
    {   

    int t_pick = Random.Range (0,5);
    int t_coat_col = Random.Range (0,5);
    int t_hat_col = Random.Range (0,5);

    MISSION[i] = new MissionTemplate();

    MISSION[i].id = i;
    MISSION[i].t_name = t_list_t[t_pick];
    MISSION[i].t_coat = t_list_c_col[t_coat_col];
    MISSION[i].t_hat = t_list_h_col[t_hat_col];
    MISSION[i].type = "Assassination";
    MISSION[i].reward1 = 0;
    MISSION[i].reward2 = "";
    }

    for (int i = 1; i <= gen; i++)
    {
    MISSION[i].ShowMission();   
    }
}

}

And:

public class MissionGen : MonoBehaviour {

    public string[] t_list_t = new string[] {"Dave", "Johnson", "Hadaki", "Tim", "Timothy", "Chris Roberts"};
    public string[] t_list_c_col = new string[] {"Blue", "Yellow", "Green", "Black", "Orange", "Purple"};
    public string[] t_list_h_col = new string[] {"Black", "Green", "Orange", "Blue", "Red", "Brown"};

Any help would be much appreciated!

Thanks,

Answer 1

This is the problem:

MissionTemplate[] MISSION = new MissionTemplate[gen];
for (int i = 1; i <= gen; i++)
{
    ...
    MISSION[i] = new MissionTemplate();

Aside from violating normal naming conventions, arrays in C# are 0-based - for example, the valid indexes for an array of length 5 are 0, 1, 2, 3 and 4.

So your for loop should be:

for (int i = 0; i < gen; i++)

Or more "obviously correctly" (IMO):

for (int i = 0; i < MISSION.Length; i++)

That makes it obvious to anyone reading the code that you're staying within the bounds of the MISSION array, without having read the array creation statement.