EditorGUI how does it work?

example. we have a simple bullet script. this script instantiating the bullet from attached prefab and gives it a start speed using rigidbody.

Bullet.cs

using UnityEngine;
using System.Collections;
public class Bullet : MonoBehaviour
{
    public GameObject bulletGameObject;
    void Start()
    {
        if (bulletGameObject.rigidbody)
        {
            GameObject newBullet = Instantiate(bulletGameObject) as GameObject;
            newBullet.rigidbody.velocity = newBullet.transform.forward * 10f;
        }
    }
}

now, let's make a custom editor, that draws a default field to select prefab, and also draws a info message - no object at all (error type), object exists but no rigidbody (error type) or just info that it's ok (info type). also, if object exists but have no rigidbody, draw a button to add rigidbody. and of course, pressing the button will add rigidbody to selected gaeobject.

BulletInspector.cs

using UnityEngine; using UnityEditor; using System.Collections; using System.Collections.Generic; [CustomEditor(typeof(Bullet))] public class BulletInspector : Editor { public override void OnInspectorGUI() { Bullet b = (Bullet)target; b.bulletGameObject = EditorGUILayout.ObjectField("bullet GO", b.bulletGameObject, typeof(GameObject), true) as GameObject; if (b.bulletGameObject) { if (!b.bulletGameObject.rigidbody) { GUI.color = new Color(1f, 0.5f, 0.5f, 1f); EditorGUILayout.HelpBox("object must have a rigidbody component", MessageType.Error, true); if (GUILayout.Button("add rigidbody to selected object")) { b.bulletGameObject.AddComponent(); } } else { GUI.color = new Color(0.5f, 1f, 0.5f, 1f); EditorGUILayout.HelpBox("object have a rigidbody component", MessageType.Info, true); }

     }
     else
     {
         GUI.color = new Color(0.5f, 0.5f, 1f, 1f);
         EditorGUILayout.HelpBox("no object selected", MessageType.Error, true);
     }
     GUI.color = Color.white;
 }

}

important

don't forget to place editor script in "Editor" folder