GameObjectExtension

using UnityEngine;
using System.Collections;
using UnityEngine.EventSystems;

public static class GameObjectExtension
{
    public static GameObject InstantiateAsChild(this Transform self, GameObject prefab)
    {
        return self.InstantiateAsChild(prefab, Vector3.zero, Quaternion.identity);
    }

    public static GameObject InstantiateAsChild(this Transform self, GameObject prefab, Vector3 position, Quaternion rotation)
    {
        var obj = GameObject.Instantiate(prefab, position, rotation) as GameObject;
        obj.transform.SetParent(self, false);
        return obj;
    }

    public static void RemoveComponent<T>(this GameObject self) where T : MonoBehaviour
    {
        T component = self.GetComponent<T>();
        if( null != component )
        {
            GameObject.Destroy(component);
        }
    }

    public static T FindComponentToRoot<T>(this GameObject self) where T : UnityEngine.Behaviour
    {
        var component = self.GetComponent<T>();
        if( null != component )
        {
            return component;
        }

        var parent = self.transform.parent;
        if( null == parent )
        {
            return null;
        }

        return parent.gameObject.FindComponentToRoot<T>();
    }

    public static GameObject FindChildRecursively(this GameObject self, string name)
    {
        foreach( Transform t in self.transform )
        {
            if( name == t.gameObject.name )
            {
                return t.gameObject;
            }

            var next = t.gameObject.FindChildRecursively(name);
            if( null != next )
            {
                return next;
            }
        }

        return null;
    }

    // call event handler recursively to all parents objects on transform hierarchy.
    public static void DoParentEventSystemHandler<T>(this Transform self, System.Action<T> action) where T : IEventSystemHandler
    {
        Transform parent = self.transform.parent;
        while (parent != null)
        {
            foreach (var component in parent.GetComponents<T>())
            {
                action((T)(IEventSystemHandler)component);
            }
            parent = parent.parent;
        }
    }
}