Can I use the new GUI system with instantiated prefabs?

I am trying to create a health bar that is controlled by a script attached to the player. I made the slider with the new UI system and is in the scene. I also have a variable called

public Slider healthSlider

When I try to drag the slider into the healthSlider field, It does not stay and, therefore, I cant control the slider as it is never referenced. Is there a way to control the slider with a c# script attached to a prefab(player)?

You can’t assign a scene object to a prefab, as prefabs are universal across scenes. What you can do is assign the value after instantiating. Pseudo code.

GameObject clone = (GameObject) Instantiate(MyPrefab);
clone.GetComponent<Slider>().value = 6;