condition in recursion - best practise

Question

hi there!

what's the best practise to break a loop? my ideas were:

Child Find(Parent parent, object criteria)
{
    Child child = null;

    foreach(Child wannabe in parent.Childs)
    {
        if (wannabe.Match(criteria))
        {
            child = wannabe;
        }
        else
        {
            child = Find(wannabe, criteria);
        }

        if (child != null) break;
    }

    return child;
}

or

Child Find(Parent parent, object criteria)
{
    Child child = null;
    var conditionator = from c in parent.Childs where child != null select c;

    foreach(Child wannabe in conditionator)
    {
        if (wannabe.Match(criteria))
        {
            child = wannabe;
        }
        else
        {
            child = Find(wannabe, criteria);
        }
    }

    return child;
}

or

Child Find(Parent parent, object criteria)
{
    Child child = null;
    var enumerator = parent.Childs.GetEnumerator();

    while(child != null && enumerator.MoveNext())
    {
        if (enumerator.Current.Match(criteria))
        {
            child = wannabe;
        }
        else
        {
            child = Find(wannabe, criteria);
        }
    }

    return child;
}

what do u think, any better ideas? i'm looking for the niciest solution :D

mo

Answer 1

There's no need for you to deal with the IEnumerator yourself, so option 3 is out.

Option 2 does not function. It continues regardless of finding a match, and if the last child is not a match and its children do not contain a match, then the result will be null even if there was a prior match.

Option 1 seems the cleanest, assuming you object to multiple return statements.

Answer 2

Linq may be more terse, but can be more difficult to understand!

    Child Find(Parent parent, object criteria)
    {
        return parent.Childs.Select(        // Loop through the children looking for those that match the following criteria
            c => c.Match(criteria)          // Does this child match the criteria?
                ? c                         // If so, just return this child
                : this.Find(c, criteria)    // If not, try to find it in this child's children
        ).FirstOrDefault();                 // We're only interested in the first child that matches the criteria or null if none found
    }