Prefabs, Classes and GameObjects. I don't understand.

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Hello,

I'm still trying to get my head around Unity's approach to OOP. Seems easy but I'm very confused with the notion of instantiating prefabs when you bring classes into the mix.

Here's my example.

I have a prefab of a planet and its pivot. The Planet gameObject has a meshFilter as a component which is just a sphere as well as a meshRenderer.

alt text

I've created a script called Planet and added this as a component to the Planet GameObject. Here's the code.

 #pragma strict
 
 public class Planet extends MonoBehaviour { 
     
     var planetName : String;//name
     var planetObject : GameObject;
     
     function Planet(name : String){
         planetName = name;
         planetObject : gameObject
     }
     
     function Start () {
     }
     
     function Update () {
     }
 }

To run things I've got an empty GameObject called Main and I've added a script component to it. Here's the code.

 #pragma strict
 
 public var planet : Planet;
 
 function Start () {
     planet   = new Planet("Earth");
 }
 
 function Update () {
 }

What I'm trying to do is create an instance of the Planet prefab (and the planetPivot) but I've completely confused myself. I know I should be using instantiate but how does that work with classes? Should I be using classes at all? I want to use a class for inheritence.

Thanks in advance!

Answer 1

Best Answer

Answer by Fattie · Mar 17, 2013 at 09:43 AM

just FYI. if you want, just don't use prefabs. I find them annoying and don't use them often.

 var newGameObject:GameObject;
 newGameObject = Instantiate( your model here );

just FWIW some discussion about making a pool , it has many Instantiate examples

http://answers.unity3d.com/questions/321762/how-to-assign-variable-to-a-prefabs-child.html

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eaj · Mar 17, 2013 at 11:53 AM 0

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Wow, that's a fantastic link and just what I needed! thanks.

I managed to get the Instantiation working but I did away with the planet class. I'll have a look at your solution next

Here's my solution.

I removed all the code from the Planet script. Essentially, for the time being, it simply holds a single variable called planetName.

And here's my main script

 #pragma strict
 
 function Start () {
     var pivot : GameObject;
     var planet : Transform;
     
     pivot  = Instantiate(Resources.Load("pivotPlanet"));
     planet = pivot.GetComponentsInChildren(Transform)[1];
     
     planet.position.y = 2;
 }
 
 function Update () {
 }

This loads the pivotPlanet asset from the Resources folder and instantiates it. From there I get the second trasform child, which is the planets transform itself. Finally as a test, I translated the planet upward in Y by 2 units.

For those with the same problem: I didn't have a Resources folder in my asset hierarchy. Resources.Load() looks in this folder for any given asset so make sure this folder exists and your assets are in there.

Answer 2

Answer by robotunity · Feb 01, 2015 at 08:29 AM

I'm still trying to get my head around Unity's approach to OOP.

This is because most Unity documentation completely ignores it. The notion of manually dragging simple things into a "scene" is heavily favored for some reason, instead of how to program a functional game.

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Prefabs, Classes and GameObjects. I don't understand.

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