Creating instances of objects in an array?

stumon · 10-19-2009, 06:54 PM

I have a Cars class already created and using a form, I am trying to create an array of classes and set each member of the array with an instance of the class. I am trying to do this within the public partial class form1 : form that Visual studio creates. I am getting an error when I try to create an instance of the class after I create the array. here is the code and the errors I am getting.

Code:

namespace VirtualRace
{
    public partial class Form1 : Form
    {
        const int RACERS = 10;
        Cars[] driver = new Cars[RACERS];
        driver[0] = new Cars("Andretti", 30, 0);
        driver[1] = new Cars("Patrick", 30, 0);
        driver[2] = new Cars("Elvers", 30, 0);
        driver[3] = new Cars("Smith", 30, 0);
        driver[4] = new Cars("Archibald", 30, 0);
        driver[5] = new Cars("Law", 30, 0);
        driver[6] = new Cars("Johnson", 30, 0);
        driver[7] = new Cars("Petty", 30, 0);
        driver[8] = new Cars("Freeman", 30, 0);
        driver[9] = new Cars("Busch", 30, 0);
        private int raceLength = 1000;
        private bool winner = false;
        private int leadLocation = 0;
        private int leadDriver = 0;
        
        public Form1()
        {
            InitializeComponent();
        }
    }
}

And the errors I am getting are: (there are these 4 errors per line starting on the driver[0] line and going till driver[9])

(16,16): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
(16,19): error CS1519: Invalid token '=' in class, struct, or interface member declaration
(16,25): error CS1520: Method must have a return type
(16,30): error CS1031: Type expected

Basically I am wondering how I can fill this array with these objects and keep them global to this class so I can use them in any Method I create? The code seems to work if I create the array and create each member within a single method, but not when I try it like this to make it available to the whole class. Any help is appreciated.

valaris · 10-20-2009, 07:15 AM

Keep

Code:

Cars[] driver = new Cars[RACERS];

at class scope, and initialize/create each object in the constructor. If you need to use these objects as early as the constructor then just construct them first thing during the constructor.

Magos · 10-20-2009, 07:39 AM

Use a list collection, and you don't have to know the size beforehand:

Code:

var driver = new System.Collections.Generic.List<Cars>();
driver.Add(new Cars("Andretti", 30, 0));
driver.Add(new Cars("Patrick", 30, 0));
driver.Add(new Cars("Elvers", 30, 0));
...

theoobe · 10-20-2009, 08:45 AM

You are not allowed to set your array's element values at class level, it must be done from within a method.

Code:

namespace VirtualRace
{
    public partial class Form1 : Form
    {
        const int RACERS = 10;
        private Cars[] driver = new Cars[RACERS];
        private int raceLength = 1000;
        private bool winner = false;
        private int leadLocation = 0;
        private int leadDriver = 0;
        
        public Form1()
        {
            driver[0] = new Cars("Andretti", 30, 0);
            driver[1] = new Cars("Patrick", 30, 0);
            driver[2] = new Cars("Elvers", 30, 0);
            driver[3] = new Cars("Smith", 30, 0);
            driver[4] = new Cars("Archibald", 30, 0);
            driver[5] = new Cars("Law", 30, 0);
            driver[6] = new Cars("Johnson", 30, 0);
            driver[7] = new Cars("Petty", 30, 0);
            driver[8] = new Cars("Freeman", 30, 0);
            driver[9] = new Cars("Busch", 30, 0);

            InitializeComponent();
        }
    }
}

stumon · 10-20-2009, 08:28 PM

Thank you guys.

arpsmack · 10-27-2009, 07:37 PM

Well, the OP probably doesn't care anymore, but I feel I should mention that you can initialize an array without using a constructor.

Code:

namespace VirtualRace
{
   public partial class Form1 : Form
   {
      Cars[] driver = new Cars[]
      {
         new Cars("Andretti", 30, 0),
         new Cars("Patrick", 30, 0),
         new Cars("Elvers", 30, 0),
         new Cars("Smith", 30, 0),
         new Cars("Archibald", 30, 0),
         new Cars("Law", 30, 0),
         new Cars("Johnson", 30, 0),
         new Cars("Petty", 30, 0),
         new Cars("Freeman", 30, 0),
         new Cars("Busch", 30, 0)
      };
      ...
   }
}

As a bonus for using this approach, you no longer have to maintain a constant for the number of racers, just use driver.Length

10-19-2009, 06:54 PM	#1
stumon eh ya hoser, got a beer? Join Date: Feb 2003 Posts: 287	Creating instances of objects in an array? I have a Cars class already created and using a form, I am trying to create an array of classes and set each member of the array with an instance of the class. I am trying to do this within the public partial class form1 : form that Visual studio creates. I am getting an error when I try to create an instance of the class after I create the array. here is the code and the errors I am getting. Code: namespace VirtualRace { public partial class Form1 : Form { const int RACERS = 10; Cars[] driver = new Cars[RACERS]; driver[0] = new Cars("Andretti", 30, 0); driver[1] = new Cars("Patrick", 30, 0); driver[2] = new Cars("Elvers", 30, 0); driver[3] = new Cars("Smith", 30, 0); driver[4] = new Cars("Archibald", 30, 0); driver[5] = new Cars("Law", 30, 0); driver[6] = new Cars("Johnson", 30, 0); driver[7] = new Cars("Petty", 30, 0); driver[8] = new Cars("Freeman", 30, 0); driver[9] = new Cars("Busch", 30, 0); private int raceLength = 1000; private bool winner = false; private int leadLocation = 0; private int leadDriver = 0; public Form1() { InitializeComponent(); } } } And the errors I am getting are: (there are these 4 errors per line starting on the driver[0] line and going till driver[9]) (16,16): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression) (16,19): error CS1519: Invalid token '=' in class, struct, or interface member declaration (16,25): error CS1520: Method must have a return type (16,30): error CS1031: Type expected Basically I am wondering how I can fill this array with these objects and keep them global to this class so I can use them in any Method I create? The code seems to work if I create the array and create each member within a single method, but not when I try it like this to make it available to the whole class. Any help is appreciated. __________________ The keyboard is the standard device used to cause computer errors!
stumon is offline

10-20-2009, 07:15 AM	#2
valaris Registered User Join Date: Jun 2008 Location: RING 0 Posts: 462	Keep Code: Cars[] driver = new Cars[RACERS]; at class scope, and initialize/create each object in the constructor. If you need to use these objects as early as the constructor then just construct them first thing during the constructor.
valaris is offline

10-20-2009, 07:39 AM	#3
Magos Confused Join Date: Sep 2001 Location: Sweden Posts: 3,122	Use a list collection, and you don't have to know the size beforehand: Code: var driver = new System.Collections.Generic.List<Cars>(); driver.Add(new Cars("Andretti", 30, 0)); driver.Add(new Cars("Patrick", 30, 0)); driver.Add(new Cars("Elvers", 30, 0)); ... __________________ MagosX.com Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime.
Magos is offline

10-20-2009, 08:28 PM	#5
stumon eh ya hoser, got a beer? Join Date: Feb 2003 Posts: 287	Thank you guys. __________________ The keyboard is the standard device used to cause computer errors!
stumon is offline

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