iterating through an array

Question

Iterating though an array isn’t a problem but what if I only wanted to incremented only when the method is called?

Im not even sure if this would work but is there an easier way of doing this

    int counter;
    string[] myArray = {"foo", "bar", "something", "else", "here"};

    private string GetNext()
    {
        string myValue = string.Empty;

        if (counter < myArray.Length) {
            myValue = myArray [counter];
        } else {
            counter = 0;
        }

        counter++;

        return myValue;
    }

I'm not sure i completely understand the question. "I only wanted to incremented only when the method is called?" — Meiscooldude
– Meiscooldude, Commented Jun 15, 2010 at 20:17
Not sure i see what you're asking really - with the exception of the initialising statements, none of this gets called unless someone calls your methond. Unless you are afraid that someone could modify either the counter or the array contents between invocations of the GetNext function... — Martin Milan
– Martin Milan, Commented Jun 15, 2010 at 20:19

Scott Chamberlain · Accepted Answer · 2010-06-15 20:28:17Z

5

What you want is an iterator

private IEnumerable<String> myEnumarable()
{
    foreach(string i in myArray)
    {
       yield return i;
    }
}

However just calling myArray.GetEnumerator(); has the same effect.

You use it by

string[] myArray = { "foo", "bar", "something", "else", "here" };
IEnumerator<String> myEnum;

private string GetNext() //Assumes there will be allways at least 1 element in myArray.
{
    if(myEnum == null)
       myEnum = myArray.GetEnnumerator();
    if(!myEnum.MoveNext())
    {
       myEnum.Reset();
       myEnum.MoveNext();
    }
    return myEnum.Current;
}

edited Jun 15, 2010 at 20:28

answered Jun 15, 2010 at 20:18

Scott Chamberlain

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Comments

Mark Byers · Accepted Answer · 2010-06-15 20:18:44Z

3

You could try this instead:

private string GetNext()
{
    string result = myArray[counter];
    counter = (counter + 1) % myArray.Length;
    return result;
}

Your code has a bug where "foo" is only returned the first time.

foo
bar
something
else
here
                <-- oops!
bar
something
else
here

answered Jun 15, 2010 at 20:18

Mark Byers

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Comments

ckramer · Accepted Answer · 2010-06-15 20:17:16Z

2

If I understand what you are wanting to do, I believe all you need to do is call the GetEnumerator() method on the array. The Enumerator object has a MoveNext() method that moves to the next item in the list, and returns true if it worked, and false if it didn't. You read the value of the enumerator with the Current property, and you can reset the counter to 0 with Reset

answered Jun 15, 2010 at 20:17

ckramer

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Dennis · Accepted Answer · 2010-06-15 21:20:28Z

The example you posted is basically an implementation of an enumerator, so yes it would work.

string[] _array = {"foo", "bar", "something", "else", "here"};

IEnumerable<String> GetEnumarable()
{
    foreach(string i in _array)
       yield return i;
}

If you want to do this with a custom data structure or want to put more logic when moving to the next element (i.e. lazy loading, streaming data) you can implement the IEnumerator interface yourself.

Example

public class EnumeratorExample : IEnumerator
{
    string[] _array;

    // enumerators are positioned before the first element
    // until the first MoveNext() call.
    int position = -1;

    public EnumeratorExample(string[] array)
    {
        _array = list;
    }

    public bool MoveNext()
    {
        ++position;
        return (position < _array.Length);
    }

    public void Reset()
    {
        position = -1;
    }

    object IEnumerator.Current
    {
        get { return Current; }
    }

    public string Current
    {
        get
        {
            try
            {
                return _array[position];
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException("Enumerator index was out of range. Position: " + position + " is greater than " + _array.Length);
            }
        }
    }
}

References
- IEnumerable Interface

Anand Kumar · Accepted Answer · 2015-06-01 11:36:54Z

0

int x=0;
while ( x<myArray.length){
    if(condition){
        x++;
        system.out.print(myArray[x]);
     }
}

answered Jun 1, 2015 at 11:36

Anand Kumar

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