Iterator and IEnumerator

Question

C#'s IEnumerator doesn't have a next() and remove() how do I solve this? (hitScans is an ArrayList)

// Iterator it = enemyWaves.iterator();
   IEnumerator it = hitScans.GetEnumerator();
         while (it.MoveNext())
            {
                if ((dist = ((ew = (EnemyWave)it.next()).distanceTraveled += ew.bulletVelocity)
                - myLocation.distance(ew.fireLocation)) > 50)
                {
                    it.remove();
                    continue;
                }

and

// Iterator i = hitScans.iterator();
   IEnumerator i = hitScans.GetEnumerator();
                while (i.MoveNext())
                {
                    double[] scan = (double[])i.next();

@PrestonGuillot IEnumerator doesn't have next() and remove(); as far as I know it doesn't have any methods similar. So what do I do to make my code work? — Jacklyn, Mar 20 '16 at 18:08

MisterMe · Accepted Answer · 2016-03-20T18:10:38.260

1

Do you realy need use Iterator/Enumerator??

If you just need to remove elements from ArrayList while iterating it (whitch is commonly discussed issue), I would propose something like this:

for (int i=hitScans.Count-1;i>=0;i--){
   if (/*your difficult condition*/){
      hitScans.RemoveAt(i);   
   }
}

and for the second part: foreach - isn't it solution?

edited Mar 20 '16 at 18:10

answered Mar 20 '16 at 18:08

MisterMe

149
10

That might work, do you know of something to replace next()? – Jacklyn Mar 20 '16 at 18:10
yep. Edited answer. foreach could help I think – MisterMe Mar 20 '16 at 18:11
Did you forget to put in the foreach version? – Jacklyn Mar 20 '16 at 18:19
I didn't put that because I didn't get what you want to get from hitScans using IEnumerator – MisterMe Mar 20 '16 at 18:21
@Jacklyn Note that with a `foreach`, you cannot modify the collection. So no removing allowed. A `for` loop does work, if you work backward (as in this answer) – Hans Keﬆing Mar 20 '16 at 20:05

score 0 · Answer 2 · edited May 23 '17 at 11:50

0

Regarding 'remove', there is no direct .NET equivalent since IEnumerable is not intended to be modifiable. There are some work-arounds: Want to remove an item from a IEnumerable<T> collection

Regarding 'next', note that even though each of 'hasNext' and 'next' are not equivalent to C# 'MoveNext' and 'Current', when used together they produce the same effect.

e.g.,

Iterator it = enemyWaves.iterator();
while (it.hasNext()) {
    Object o = it.next();
}

will typically convert to the following C# code:

IEnumerator it = enemyWaves.GetEnumerator();    
while (it.MoveNext())
{
    object o = it.Current;
}

edited May 23 '17 at 11:50

Community

1
1

answered Mar 20 '16 at 18:41

Dave Doknjas

6,394
1
15
28

Thank you, but it seems I have to use a for loop as MisterMe said – Jacklyn Mar 20 '16 at 18:46
@Jacklyn: Yes - I don't think you can remove an item in the standard MoveNext/Current loop. – Dave Doknjas Mar 20 '16 at 18:48

Iterator and IEnumerator

2 Answers2