ComponentExtensions.cs

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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License. See LICENSE in the project root for license information.

using System;
using System.Collections.Generic;
using UnityEngine;

namespace HoloToolkit.Unity
{
    public static class ComponentExtensions
    {
        public static T EnsureComponent<T>(this GameObject gameObject) where T : Component
        {
            T foundComponent = gameObject.GetComponent<T>();
            if (foundComponent == null)
            {
                return gameObject.AddComponent<T>();
            }

            return foundComponent;
        }

        public static T EnsureComponent<T>(this Component component) where T : Component
        {
            return EnsureComponent<T>(component.gameObject);
        }

        public static void ApplyToHierarchy(this GameObject root, Action<GameObject> action)
        {
            action(root);
            foreach (var item in root.GetComponentsInChildren<Transform>())
            {
                action(item.gameObject);
            }
        }

        public static T FindAncestorComponent<T>(this GameObject gameObject, bool includeSelf = true) where T : Component
        {
            return gameObject.transform.FindAncestorComponent<T>(includeSelf);
        }

        public static T FindAncestorComponent<T>(this Component component, bool includeSelf = true) where T : Component
        {
            return component.transform.FindAncestorComponent<T>(includeSelf);
        }

        public static T FindAncestorComponent<T>(this Transform startTransform, bool includeSelf = true) where T : Component
        {
            foreach (Transform transform in startTransform.EnumerateAncestors(includeSelf))
            {
                T component = transform.GetComponent<T>();
                if (component != null)
                {
                    return component;
                }
            }

            return null;
        }

        public static IEnumerable<Transform> EnumerateAncestors(this Transform startTransform, bool includeSelf)
        {
            if (!includeSelf)
            {
                startTransform = startTransform.parent;
            }

            for (Transform transform = startTransform; transform != null; transform = transform.parent)
            {
                yield return transform;
            }
        }

        public static void ForEachComponent<T>(this GameObject g, Action<T> action)
        {
            foreach (T i in g.GetComponents<T>())
            {
                action(i);
            }
        }
    }
}