Unity扩展GameObject等类中的方法

public static class Assist   {

    public static T AddComponentSingle<T>(this GameObject gameObject) where T : Component
    {
        return addcomponentSingle<T>(gameObject);
    }

    public static T AddComponentSingle<T>(this Transform transform) where T : Component
    {
        return addcomponentSingle<T>(transform.gameObject);
    }

    private static T addcomponentSingle<T>(GameObject target) where T : Component
    {
        if (target.GetComponent<T>() != null)
        {
           GameObject.Destroy(target.GetComponent<T>());
        }
        return target.AddComponent<T>();
    }
}