get component by interface from gameobject

extension

  	public static T GetComponentByInterface<T>(this GameObject go) where T : class
        {
            var components = go.GetComponents<MonoBehaviour>();
            foreach (var c in components)
            {
                T t = c as T;
                if (t != null)
                    return t;
            }
            return null;
        }

        public static T[] GetComponentsByInterface<T>(this GameObject go) where T : class
        {
            var components = go.GetComponents<MonoBehaviour>();
            var list = new List<T>();
            foreach (var c in components)
            {
                T t = c as T;
                if (t != null)
                    list.Add(t);
            }
            return list.ToArray();
        }

gistfile1.cs

public class TapableImpl : ITapable 
{
	public void Tapped()
        {
        }
}

interface

    public interface ITapable
    {
        void Tapped();
    }

use case

 var tapable = hit.collider.gameObject.GetComponentByInterface<ITapable>();