Instantiate GameObject with parameters

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How do I instantiate a GameObject with parameters? In traditional programming parlance, how do I new a GameObject with a non-parameter-less constructor?

Obviously I can do this:

 GameObject go = Instantiate(Resources.Load("Spot")) as GameObject;
 go.transform.position = new Vector3(42, 42, 42);

But updating all the properties individually is tedious and requires the writing of many setters. Is there a way to instantiate with parameters, akin to

 Spot go = new Spot(new Vector3(42, 42, 42);

And - ideally - is there a way to "overload that constructor" to allow for different instantiation scenarios? Is there a way to pass along parameters to the objects constructor or to the Start() function?

Answer 1

Best Answer

Answer by hathol · May 18, 2012 at 02:42 PM

try that:

 public static Object prefab = Resources.Load("Prefabs/YourPrefab");
 public static YourComponent Create()
 {
     GameObject newObject = Instantiate(prefab) as GameObject;
     YourComponent yourObject = newObject.GetComponent<YourComponent>();

     //do additional initialization steps here

     return yourObject;
 }

and then overload and parametrize your create function as much as you like :)

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hathol · May 18, 2012 at 02:47 PM 0

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That code goes into the script of the object you want to create of course and can be called like

YourComponent bla = YourComponent.Create();

Drakestar · May 20, 2012 at 05:39 AM 0

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+1, been toying around with a similar idea.

Guirao · Jan 17, 2013 at 11:27 AM 1

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Do you have to assign the script to the prefab?

svendkiloo · Dec 05, 2018 at 07:25 AM 2

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You don't, at least in newer Unity versions, have to GetComponent. If your prefab is of the type of the script (Resources.Load has a generic version), then Instantiate will return an object of the same type, so you'll have the script already. Just as a side note: Don't use Resources ;) (2.1. Best Practices for the Resources System: Don't use it.)

Ziplock9000 · Mar 01, 2019 at 03:33 PM 1

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This does not instantiate the GO with parameters. In the instantiate call the object is fully created and awake is called. So any values you might have wanted to pass in as a construction parameters you can't. The object has already been made by the time you get to your GetComponent line.

svendkiloo Ziplock9000 · Mar 04, 2019 at 07:33 AM 0

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I would post another answer, but as one has been suggested, I'm not allowed (another reason Unity Answers is inferior to SO). One option, if the initialisation values are or could be serialisable, would be to set them on the prefab before instantiation. This isn't ideal, but it's a way around not being able to set custom values (other than position, scale and rotation) with the creation of a game object.

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Answer 2

Answer by MithosAnnar · May 17, 2012 at 08:19 PM

Easy Peasy.

 public GameObject spot;
 
 public Vector3 v = new Vector3(42, 42, 42);
 
 GameObject go = Instantiate(spot, new Vector3(0, 0, 0), Quaternion.identity) as GameObject;
 
 go.SendMessage("TheStart", v);

On the script attached to your spot:

 void TheStart (Vector3 v) {   // you can't use start. But this is just as good.
 
     transform.position = v;
 
 }

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Drakestar · May 18, 2012 at 03:03 AM 0

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I'm assu$$anonymous$$g that you mean go.Send$$anonymous$$essage(). Cool, this works "well enough". I wasn't aware of this and kept retrieving the script via GetComponent first, which is cumbersome.

Drakestar · May 18, 2012 at 03:09 AM 0

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Looks like spoke too soon, as Send$$anonymous$$essage only allows one argument. There's hacks around this, but creating and extracting arrays isn't nearly as neat as actual ctor functionality.

syclamoth · May 18, 2012 at 03:40 AM 1

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I usually use 'messenger' classes that contain all the parameters I need. I then simply send the newly constructed 'messenger' as the single parameter of Send$$anonymous$$essage.

MithosAnnar · May 18, 2012 at 08:05 AM 0

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you could just send multiple messages. I do because sending messages is fast and neat.

syclamoth · May 18, 2012 at 08:19 AM 0

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Sending one message is still faster than sending several.

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Instantiate GameObject with parameters

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