Question

I have a recursive method that builds a tree-like structure of a resource and its related resources.

For each resource that I work with I add it to a class member list which I check on each iteration to make sure that we don’t loop infinately on resources that are inter dependent.

Each time I call this recursive method for the first time, I need the class member list to be clear.

At the moment I have a seperate method to do this which I can call between calls to the recursive method.

I’d like to get rid of this method call and reset the list automatically each time.

At the moment I can see two options to solve this problem:

1. Test whether the calling method is the same as the currently
   executing method and if not, reset the list
2. Get rid of the recursion and queue items instead, dequeueing and
   enqueueing as we go. At the end of the method call I can reset the list.

How would you go about solving this problem? What approach would you take?

Here’s how my code currently looks:

public class GetAllRelatedResourcesByParentGuidQuery : IGetAllRelatedResourcesByParentGuidQuery
    {
        private readonly IList<Guid> _itemsCheckedForRelations = new List<Guid>();

        public IEnumerable<IDependency> Invoke(Guid parentCiId, 
                                                  IResoucesByIdQuery getResources)
        {
            if (!_itemsCheckedForRelations.Contains(parentCiId))
            {
                var relatedResources = getResources.Invoke(parentCiId);

                _itemsCheckedForRelations.Add(parentCiId);

                if (relatedResources.Count() > 0)
                {
                    foreach (var relatedResource in relatedResources)
                    {
                        relatedResource.Resource.DependentResources = Invoke(
                                                         relatedResource.Resource.Id, 
                                                         getResources);

                        yield return relatedResource;
                    }
                }
            }
        }

        public void ResetCheckedItemsCollection()
        {
            _itemsCheckedForRelations.Clear();
        }
    }

Answer 1

I would make a public method which performs the creation, but make the recursive method not care, and take it as a parameter.

public List<string> DoSomething(int input)
{
    List<string> results = new List<string>();
    DoSomethingImpl(input, results);
    return results;
}

private void DoSomethingImpl(int input, List<T> results)
{
    // For example...
    if (input == 0)
    {
        return results;
    }
    results.Add("Foo");
    DoSomethingImpl(input - 1, results);        
}