using Switch in for loop

Question

I have already received this problem a few times, i wonder why i can't use my index in the switch, i receive an error that the array[index] = null, any reason why?

// array of classes, im using public getters and setters to access the rank and cardcolor
Cardgame[] cardgame = new Cardgame[50];
int index = 0;
string CardColor = "";

...             

for (int i = 0; i < 4; i++)
{
    switch (i)
    {
        case 1: CardColor = "red";
            break;
        case 2: CardColor = "blue";
            break;
        case 3: CardColor = "diamond";
            break;
        case 4: CardColor = "candy!";
            break;
    }
    for (int x = 0; x <= 13; x++)
    {
        index++; 
     Cardgame[index].Color = CardColor;
        switch (x)
        {

            default: Cardgame[index].Number = x.ToString();
                break;
            case 11: Cardgame[index].Number = "Farmer";

                break;
            case 12: Cardgame[index].Number = "Queen";

                break;
            case 13: Cardgame[index].Number = "King";

                break;
        }
    }

new Cardgame[50] initializes a Cardgame array with 50 nulls. Are you creating 50 new Cardgames to fill the array after that? — Ry-
– Ry- ♦, Commented Aug 12, 2013 at 23:03
for (int i = 0; i <= 4; i++) should be for (int i = 1; i <= 4; i++) — Blorgbeard
– Blorgbeard, Commented Aug 12, 2013 at 23:05
you missing Cardgame[index]= new CardGame();You have to create the object before u use it — Dan Hunex
– Dan Hunex, Commented Aug 12, 2013 at 23:07
thank you for your support Dan Hunex, i'm really grateful that you take your time to help someone who has a stupid beginner question. — Cedric Della faille
– Cedric Della faille, Commented Aug 12, 2013 at 23:18

ChrisWue · Accepted Answer · 2013-08-12 23:04:16Z

3

Because you have an array of Cardgame objects. The default array initializer will set all objects to null. You have to do a cardgame[index] = new Cardgame() first.

answered Aug 12, 2013 at 23:04

ChrisWue

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Austin Salonen · Accepted Answer · 2013-08-12 23:21:26Z

// first define the possible values
var suits = new [] {"red", "blue", "diamond", "candy"};
var ranks = new [] {"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "farmer", "queen", "king"}

//var ranks = Enumerable.Range(1, 10).Select(n => n.ToString())
//                      .Concat(new [] {"farmer", "queen", "king"})
//                      .ToArray();

// given the known values, you just iterate over every possible index
for(int i = 0; i < suits.Length * ranks.Length; i++)
{
    Cardgame[i] = new CardGame();
    Cardgame[i].CardColor = suits[i % suits.Length];
    Cardgame[i].Number = ranks[i / ranks.Length];
}

// or some "harder" LINQ    
var Cardgame = (from s in suits
               from r in ranks
               select new CardGame(s, r)).ToArray();

this is quite interesting, instead of using a nested loop, i could try it in another way.

alanmanderson · Accepted Answer · 2013-08-12 23:10:27Z

0

You are iterating through the first loop 5 times and iterating through 14 cards each time... That is 70 cards.

Also, you are never initializing any of the cardgame objects.

you want to do:

for (int i = 0; i < 4; i++)
{
    ...
    for (int x = 0; x < 13; x++)
    {
        Cardgame[index] = new Cardgame();            
        ...
        index++;
    }
    ...
}

edited Aug 12, 2013 at 23:10

answered Aug 12, 2013 at 23:04

alanmanderson

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2 Comments

alanmanderson Over a year ago

You need to change the second loop as well. Either by starting at 0 or ending at 12... which means you would want to change your switch statement as well.

Cedric Della faille Over a year ago

Thank you very much i just started to learn about arrays and i'm still have some green behind my ears about what is classes. i thank you for your help. I hope this will help others as well, this might prevent others for looking for hours what might have gotten wrong in your loop.

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