c# Initializing array of certain by using method

Question

I am trying to initialize a newly created empty array by using a method. Example below. This is the structure of the code that I want to create.

var v = exClass[5,5];
v.ExtensionMethodThatWillInitilize();

What I want ExtensionMethodThatWIllInitilize to do is following:

for(int y = 0 ; y < exClass.getLength(0); y++ ) {
for(int x = 0 ; x < exClass.getLength(1); x++ ) {
v[y,x] = new instanceObject();
}}

So I came up with below code...

namespace ConsoleApplication1
{
class Program
{
    static void Main(string[] args)
    {
        var oldEx = new ExClass[10, 10];
        var newEx = oldEx.init();
    }
}
public class ExClass
{
    public string exString
    public ExClass() {
    exString = " I AM NEW! YES! ";
 }
}
public static class tools
{
    static public ExClass[,] init(this ExClass[,] start)
    {
        var newArray = new ExClass[start.GetLength(0), start.GetLength(1)];
        for (int y = 0; y < start.GetLength(0); y++)
        {
            for (int x = 0; x < start.GetLength(1); x++)
            {
              newArray[y, x] = new ExClass();
            }
        }
        return newArray;
    }
}

Yet the problem is that I do not know how to modify my init method so that it can take any type of array and return corresponding array that had been initialize. I tried to use generic type T but my lack of experience seems to fail.

Summery:

1) how do you come up with a method that will initialize an empty array in a single step.

2) how do you make sure that the method can initialize any type of array(assuming that the element in the array has a constructor that does not take any argument)

Try posting your attempt at a generic method, because that most certainly is the solution to this. I'm pretty sure where you went wrong, but it's better to not guess. — Servy
– Servy, Commented Feb 23, 2012 at 18:21

Steve Konves · Accepted Answer · 2013-02-11 18:57:18Z

1

Generics do work. You need to declare your method as a generic type.

I have modified the above example as follows:

class Program
{
    static void Main(string[] args)
    {
        var oldEx = new ExClass[10, 10];
        var newEx = oldEx.init<ExClass>();
    }
}
public class ExClass
{
    public string exString = "I AM NEW";
}
public static class tools
{
    static public T[,] init<T>(this T[,] start)
    {
        var newArray = new T[start.GetLength(0), start.GetLength(1)];
        for (int y = 0; y < start.GetLength(0); y++)
        {
            for (int x = 0; x < start.GetLength(1); x++)
            {
                newArray[y, x] = Activator.CreateInstance<T>();
            }
        }
        return newArray;
    }
}

As an answer to your comment below:

class Program
{
    static void Main(string[] args)
    {
        var oldEx = tools.init<ExClass>(10, 10);

    }
}
public class ExClass
{
    public string exString = "I AM NEW";
}
public static class tools
{
    static public T[,] init<T>(int x,int y)
    {
        var newArray = new T[x, y];
        for (int i = 0; i < x; i++)
        {
            for (int j = 0; j < y; j++)
            {
                newArray[i, j] = Activator.CreateInstance<T>();
            }
        }
        return newArray;
    }
}

edited Feb 11, 2013 at 18:57

Steve Konves

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answered Feb 23, 2012 at 18:24

Manas

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7 Comments

BlueBug Over a year ago

Would it be possible to have the init method to directly modify original 'start'?

BlueBug Over a year ago

so that I do not need to reassign the whole thing over again?

BlueBug Over a year ago

+1 vote, I will try to post more details that I wana know but I gotta go to class soon! thank you so much for this modification!

Manas Over a year ago

Yes it is possible, but you need to pass both the arguments as parameter. I have edited my answer above and added the code for your requirement.

Servy Over a year ago

Why use reflection when you can just constrain T to have a default constructor?

|

Avner Shahar-Kashtan · Accepted Answer · 2012-02-23 18:25:05Z

1

Check out this generic method, which uses the new generic constraint:

 static public void Init<T>(this T[,] array) where T : new()
 {
    for (int y = 0; y < array.GetLength(0); y++)
    {
       for (int x = 0; x < array.GetLength(1); x++)
       {
          array[y, x] = new T();
       }
    }
  }

The main differences from your code are:

1) The method is Init to specify a generic parameter, and there where T : new() constraint ensures that we can call new T();

2) Instead of returning a new, initialized array, I'm simply initializing the array in-place. Seems more logical. If you want, you can use your original version, but I don't understand why you'd need to.

answered Feb 23, 2012 at 18:25

Avner Shahar-Kashtan

14.8k3 gold badges42 silver badges66 bronze badges

1 Comment

BlueBug Over a year ago

Thank you so much for this version of code. I am eternally happy to initialize my array with this method! your code will live in my extensions class FOREVER!

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