Tree.ReflectClassForwards (GameObject) and Tree.SetForwards (int id, IActionClass actionClass). This is now built-in per Behave 2.6.

BehaveExtensions.cs

using UnityEngine;
using Behave.Runtime;
using Library = BLYourLibraryName;
using Tree = Behave.Runtime.Tree;


public interface IActionClass
{
	bool OnForward (Tree sender);
	BehaveResult Init (Tree sender);
	BehaveResult Tick (Tree sender);
	void Reset (Tree sender);
}


public static class BehaveExtensions
{
	static readonly string s_IActionTypeName = typeof (IActionClass).Name;
	const string kActionClassPostfix = "Action";


	public static void ReflectClassForwards (this Tree tree, GameObject gameObject)
	{
		foreach (MonoBehaviour behaviour in gameObject.GetComponents<MonoBehaviour> ())
		{
			System.Type type = behaviour.GetType ();

			if (type.GetInterface (s_IActionTypeName) == null)
			{
				continue;
			}

			string name = type.Name;
			int actionIndex = name.IndexOf (kActionClassPostfix);
			if (actionIndex < 1)
			{
				Debug.LogError (string.Format (
					"Bad {0} type name (format is \"[Name]{1}\"): {2}",
					s_IActionTypeName,
					kActionClassPostfix,
					name
				));
				continue;
			}
			name = name.Substring (0, actionIndex);

			int id = 0;

			try
			{
				id = (int)System.Enum.Parse (typeof (Library.ActionType), name);
			}
			catch
			{
				Debug.LogError ("Unknown action type: " + name);
				continue;
			}

			tree.SetForwards (id, (IActionClass)behaviour);
		}
	}


	public static bool SetForwards (this Tree tree, int id, IActionClass actionClass)
	{
		// TODO: When Tree.ActionIDs has been implemented, we should first check if tree.ActionIDs contains id - returning false if not

		if (!actionClass.OnForward (tree))
		{
			return false;
		}
		
		tree.SetInitForward (id, actionClass.Init);
		tree.SetTickForward (id, actionClass.Tick);
		tree.SetResetForward (id, actionClass.Reset);

		return true;
	}
}