Unity attaching GameObjects to scripts as a class

Question

About a month into making my first game, I have realized that I am very confused when it comes to attaching gameobjects as classes to another game object's script. That's a mouthful so here's my issue.

My Game.cs attached to Game (gameobject) has

public Player player;

My Player.cs is attached to a Player (gameobject) prefab

Why can I drag a Player gameobject, that has a player script, into the Game gameobject's "player" field? How does that make sense? It should be

public GameObject player;

Then I would drag my prefab gameobject "Player".

The reason why this confuses me is, If i Instantiate "player", am I instantiating a gameobject? It seems not, because I cannot do this:

GameObject newPlayer = Instantiate(player, new Vector3(1,1,1), Quaternion.identity) as GameObject;
newPlayer.transform.SetParent(GameObject.Find("Level"));

If I do I will get the error the newPlayer is null.

what unity actually is doing is trying to be nice. Dragging a game object into that public Player player; property Unity is analyzing the GameObject for components that would fit into the variable and getting the player one for you. You are not actually putting a GameObject (Square Peg) into a Player variable (Round Hole). I beleive if you tried to put a game object there that didn't have a component of the Player Class Unity would silently fail. — Joe

Geri Borbás Geri Borbás · Accepted Answer · 2015-05-18T23:35:54

A script is actually a Component object like any other object (most of the time).

It is technically not too easy to drag a Component object from an inspector onto another slot in another inspector. Probably thats why they made this "shorthand", when you can drag the actual GameObject instead from the hierarchy.

If the dragged GameObject has a matching component to a slot, it counts as you have dragged the Component itself.

You cannot instantiate a script Component using Object.Instantiate, you'll always instantiate a GameObject this way, see the docs. If you need the script, simply get the component from the brand new instance.

It can be confusing indeed, I personally prefer naming convention something like:

public GameObject playerObject;
public Player player;

Unity attaching GameObjects to scripts as a class

2 Answers