How to run code when an object is placed in the editor?

Questions & Answers
1

I’m building a 2D game where the action happens in the x-z plane. When working in the editor and placing an object in my scene, the objects get unpredictable Y values which I then have to correct to 0 so that they look correct in the editor (I have attached a script to them which guarantees y=0 in PLAY mode). How can I ensure that all my objects are placed with y=0? My idea was to attach a component with a script to my prefab and then place objects via prefab, but I don’t know how to make a script attached to an object run code in the editor at the time the object is placed in the scene.

2

There are MonoBehaviours that you can instruct to run while in Editor mode:

Just write a MonoBehaviour like in this example:

Another way (which I do not recommend, but will still work) is to abuse a function that is called in Editor Mode to execute your script, such as OnDrawGizmos().

I don’t know how you could correct your gameObject in the exact moment you are placing them in the Editor, but I think you could set the y position of every gameObject in your scene (or only of the desired gameObjects) to 0 in every update. An update in the Editor mode occurs if there is a user input, such as a mouse movement or click.

In your code you could write something like:

var gameObjects = GameObject.FindObjectsOfType<YourType>();
foreach (var object in gameObjects) }{
   object.transform.position = new Vector3(object.transform.position.x, 0, object.transform.position.z);
}