Thread: Why use indexers?

Hi!

Can someone enlighten me as to when, where, and why one would use a class indexer? I am trying to come up with an example which features the benefits of indexers--and am coming up dry. Is there more to it than saving a method declaration? So, please share with me what they are actually used for and what the benefit is.

Jess

C# Online.NET

http://wiki.csharp-online.net/

Yes, what I am trying to say is that in the examples I've seen, I can see no advantage to using an indexer vs. using regular method calls. So what am I missing?

In the tutorial (http://msdn.microsoft.com/library/de...stutorial.asp), for example, one can *already* access the file as a byte array, so why write a class to do so?

Just an example--sure; but, that's what I am saying: Where are the good examples that have real benefits?

Just an alternative--okay; but, why would I choose this alternative?

If indexers are for "array-like" abstractions, why not use an array?

Jess

C# Online.NET

http://wiki.csharp-online.net/

Code:

namespace Enviroment1
{
    public class Test
    {
        public static void Main( )
        {
            int numberOfArrays = 5;
            MyCollecionClass mcc = new MyCollecionClass(numberOfArrays);
            mcc[0] = "one";
            mcc[1] = "two";
            mcc[2] = "three";
            mcc[3] = "four";
            mcc[4] = "five";

            for ( int i = 0; i < numberOfArrays; ++i )
            {
                Console.WriteLine(mcc[i]);
            }
        }
    }

    public class MyCollecionClass
    {
        private string[] array;

        public MyCollecionClass( int arrayLength )
        {
            array = new string[arrayLength];
        }

        public string this[int index]
        {
            get
            {
                if ( (index >= 0) && (index < array.Length) )
                {
                    return array[index];
                }

                Console.WriteLine("out of bounds!");
                return null;
            }
            set
            {
                if ( (index >= 0) && (index < array.Length) )
                {
                    array[index] = value;
                }
            }
        }
    }
}

I don't know about you, but, to me this indexer is much more easier and intuitive than, say, create a method as you suggested. How would you do it with a method?

The code below does the same thing without an indexer.

I am not really arguing against indexers--I just don't get the point. I wish someone sympathetic to indexers would write an article on them for us. I am afraid I won't do them justice.

Jess

C# Online.NET

http://wiki.csharp-online.net/

Code:

public class Test
    {
        public static void Main( )
        {
            int numberOfArrays = 5;
            MyCollectionClass mcc = new MyCollectionClass(numberOfArrays);
            mcc.set(0, "one");
            mcc.set(1, "two");
            mcc.set(2, "three");
            mcc.set(3, "four");
            mcc.set(4, "five");

            for ( int i = 0; i < numberOfArrays; ++i )
            {
                Console.WriteLine(mcc.get(i));
            }
         }
    }

    public class MyCollectionClass
    {
	 private string[] array;

	 public string get (int index) { return array[index]; }
	 public void   set (int index, string value) { array[index] = value; }

        public MyCollectionClass ( int arrayLength )
        {
            array = new string[arrayLength];
        }

    }

Actually, I would make the same argument about properties as opposed to simply using accessors and mutators to encapsulate. To me, they both seem like guilding the lily.

Jess

C# Online.NET

http://wiki.csharp-online.net/