Initialize array of a class with fixed length and dynamically add values in C#

Question

I want to have a two-dimensional game board, and every field is a custom class with information about this field, with properties. The size of the game board is known on instantiation, the values of the properties are not. After instantiation, I want to randomly set them for each field. My initial idea was to create an array, not a list, because the size of the game board is always fixed.

public class GameBoard
{
    private int _xValue;
    private int _yValue;
    private int _bombs;

    private int _fields;

    public Field[][] gameBoard;

    public GameBoard(int x, int y)
    {
        _xValue = x;
        _yValue = y;
        _fields = _xValue * _yValue;

        gameBoard = new[] { new Field[_xValue], new Field[_yValue] };
    //Here I have to initialize every Field

        for (int i = 0; i < _xValue; i++)
        {
            for (int j = 0; j < _yValue; j++)
            {
                //Set properties of Field
                //For example: gameBoard[i][j].IsBomb = RandomBoolean;
                //Here I get NullReferenceExceptions
            }
        }
    }
}

I do understand why this does not work. I tried lists, two-dimensional arrays or, like at the moment, a jagged array, what I would prefer. How can I solve this problem in a readable, clean way?

EDIT

The Field class:

public class Field
{
    public bool IsBomb { get; set; }
    public bool IsFlagged { get; set; }
}

I tried to add gameBoard[i][j] = new Field(); inside the nested forloop. This leads to an IndexOutOfRangeException.

Since Field is a class then after gameBoard = new[] { new Field[_xValue], new Field[_yValue] }; you have a jagged array of nulls - you need to new them in your loop — UnholySheep
– UnholySheep, Commented Dec 30, 2019 at 17:38
Yes, Field is a class, I will edit my question. I tried gameBoard[i][j] = new Field();, in the nested for loop. Then I get: IndexOutOfRangeException — Lukas
– Lukas, Commented Dec 30, 2019 at 17:41
You can use a List and convert it to Array after adding an items — Pavel Anikhouski
– Pavel Anikhouski, Commented Dec 30, 2019 at 17:51
@PavelAnikhouski Why would you use a List at all? There is no need. — user12447201
– user12447201, Commented Dec 30, 2019 at 17:52

Roman.Pavelko · Accepted Answer · 2019-12-30 17:51:52Z

2

Here is your array-property:

public Field[,] gameBoard;

And here is initialization:

public GameBoard(int x, int y)
{
    _xValue = x;
    _yValue = y;
    _fields = _xValue * _yValue;

    gameBoard = new Field[_xValue, _yValue];
    for (int i = 0; i < _xValue; i++)
    {
        for (int j = 0; j < _yValue; j++)
        {
            gameBoard[i, j] = new Field();
        }
    }
 }

answered Dec 30, 2019 at 17:51

Roman.Pavelko

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Comments

Wai Ha Lee · Accepted Answer · 2019-12-31 00:24:48Z

1

Lots of confusion in here on how to work with jagged arrays. If you want to work with jagged arrays, you have to setup in such a way

//Declare jagged array, I want _xValue arrays
Field[][] gameBoard = new Field[_xValue][];

for (int i = 0; i < _xValue; i++)
{
    gameBoard[i] = new Field[_yValue];
    for (int j = 0; j < _yValue; j++)
    {
        gameBoard[i][j] = new Field(){ IsBomb = RandomBoolean};
    }
}

The equivalent in a multi-dimensional array would be

//Declare multi-dimensional array of size _xValue x _yValue
Field[,] gameBoard2 = new Field[_xValue, _yValue];

for(int i = 0; i < _xValue; i++)
{
    for(int j = 0; j < _yValue; j++)
    {
        // Instantiate the Field object at x,y
        gameBoard2[i, j] = new Field { IsBomb = RandomBoolean };
    }
}

edited Dec 31, 2019 at 0:24

Wai Ha Lee

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answered Dec 30, 2019 at 18:08

user12447201

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