How can I make a custom editor that creates/deletes game object clones around a given point

Question

I have been manually creating and deleting clones of my game objects that I arrange in a circle around a given point. Each of the objects is rotated making each object the same angle apart from the others as seen in the image below.

My objects range from 2 to 10. Doing this manually is very cumbersome, especially when changes have to made. How can I create a unity custom editor that allows me to specify a number of game object clones I want to create around a specified anchor point? Additionally, adjusting the number of clones should dynamically create/delete clones and reposition/rerotate them.

Answer 1

Make an object and position at the center of your circle. If you already have an object with a custom script there, make an Inspector for it. If you don't have anything, make a script. It doesn't have to do anything. It might just hold data. A custom inspector just needs an script. Let's call them CircleSpawn and CircleSpawnEditor. CircleSpawn gets attached to the object at the center of the circle. It might look like this:

public class CircleSpawn : MonoBehaviour {
    public float radius;
    public int numOfItems;
    public GameObject clonedObject;
    public List<GameObject> spawnedObjects;
}

CircleSpawnEditor needs to be saved to a folder called Editor and looks something like this:

using UnityEngine;
using System.Collections.Generic;
using UnityEditor;

[CustomEditor(typeof(CircleSpawn))]
public class CircleSpawnEditor : Editor
{

    public override void OnInspectorGUI()
    {
        var tar = (CircleSpawn)target;

        //set its values
        tar.radius = EditorGUILayout.FloatField("Radius:", tar.radius);
        tar.numOfItems = EditorGUILayout.IntField("Number of Items:", tar.numOfItems);
        tar.clonedObject = (GameObject)EditorGUILayout.ObjectField(tar.clonedObject,
                       typeof(GameObject), true);

        //Inspector button for creating the objects in the Editor
        if (GUILayout.Button("Create"))
        {

            //clean up old objects
            if (tar.spawnedObjects != null)
            {
                foreach (var ob in tar.spawnedObjects)
                {
                    DestroyImmediate(ob);
                }
            }
            tar.spawnedObjects = new List<GameObject>();

            float angleBetween = 360.0f / tar.numOfItems;
            float angle = 0;
            for (int i = 0; i <= tar.numOfItems; i++)
            {
                //for each object, find a rotation and position
                var rot = Quaternion.Euler(0, angle, 0);
                var localPos = rot * Vector3.forward * tar.radius;
                tar.spawnedObjects.Add(Instantiate(tar.clonedObject,
                    tar.transform.position + localPos, rot));
                angle += angleBetween;
            }
        }
    }
}

I tested it and the result looks like this: