How to use LINQ to select all descendants of a composite object

Question

How can I make ComponentTraversal.GetDescendants() better using LINQ?

Question

public static class ComponentTraversal
{
    public sta         


        

Answer 1

There are often good reasons to avoid (1) recursive method calls, (2) nested iterators, and (3) lots of throwaway allocations. This method avoids all of those potential pitfalls:

public static IEnumerable GetDescendants(this Composite composite)
{
    var stack = new Stack();
    do
    {
        if (composite != null)
        {
            // this will currently yield the children in reverse order
            // use "composite.Children.Reverse()" to maintain original order
            foreach (var child in composite.Children)
            {
                stack.Push(child);
            }
        }

        if (stack.Count == 0)
            break;

        Component component = stack.Pop();
        yield return component;

        composite = component as Composite;
    } while (true);
}

And here's the generic equivalent:

public static IEnumerable GetDescendants(this T component,
    Func hasChildren, Func> getChildren)
{
    var stack = new Stack();
    do
    {
        if (hasChildren(component))
        {
            // this will currently yield the children in reverse order
            // use "composite.Children.Reverse()" to maintain original order
            // or let the "getChildren" delegate handle the ordering
            foreach (var child in getChildren(component))
            {
                stack.Push(child);
            }
        }

        if (stack.Count == 0)
            break;

        component = stack.Pop();
        yield return component;
    } while (true);
}