How do you instantiate a script from a monoscript?

Question

I'm making en editor tool to create prefabs from selected scripts. Selection.objects returns a list of objects which are actually monoscripts. Monoscripts can't seem to be cast as anything, and while I can use GetClass() to find the type, I don't know how to use that type to instantiate a new, properly casted script object. Instantiate(obj) as ScriptName returns a null, and I can't figure out how to fit the returned (GetClass()) type into a New() method, since unity doesn't register that as a type.

Important note: This class doesn't derive from monobehaviour. Previous it did, and I was using AddComponent<((Monoscript)obj).GetClass()>(), but since then I've discovered I need it to be a custom class.

Here's the entire, currently mangled script so you can see what I'm doing:

 using UnityEngine;
 using UnityEditor;
 using System.IO;
 using System.Collections;
 
 public class CreateItemPrefabs : EditorWindow {
 
     [MenuItem ("Tools/Create Item Prefabs")]
     static void CreatePrefabs ()     // goes through each script selected in the editor and creates a prefab
     {
         foreach (Object obj in Selection.objects)
         {
 
             var go = new GameObject();
             //System.Type itemType = ((MonoScript)obj).GetClass();
             Item instance = Instantiate( obj) as Item;
 
             var container = go.AddComponent<ItemContainer>();
             container.m_Item = instance;
             Debug.Log(instance.GetType());
             Item _item = go.GetComponent<Item>();
 
             if( !(instance is Item))
             {
                 Debug.Log("skipped");
                 continue;
             }
 
             // Add interactive script and tag it
             var pickupScript = go.AddComponent<InteractData>();
             pickupScript.interactTag = "Item";
             pickupScript.hoverMessage = "pick up " + _item.itemName;
 
             // Change tag to interact
             go.tag = "Interact";
 
 
             Object prefab = AssetDatabase.LoadAssetAtPath("Assets/Prefabs/Items/"+obj.name+".prefab", typeof(Object));
 
             // if no prefab is found, create one.
             if (prefab == null)
             {
                 prefab = PrefabUtility.CreateEmptyPrefab("Assets/Prefabs/Items/"+obj.name+".prefab");
             }
 
             // Replace prefab
             PrefabUtility.ReplacePrefab(go, prefab, ReplacePrefabOptions.ReplaceNameBased);
             DestroyImmediate(go);
         }
     }
 }

Answer 1

Answer by aidesigner · Oct 10, 2014 at 11:43 AM

Here are your options depending on your base class. Since .NET is a statically typed language you must know a common base that all your instances will share. Note .Net has recently added great support for the dynamic type, but it is a long way from making it to Unity (Mono 2.6).

Base Class System.Object:

MyCommonClass myCommonClass = Activator.CreateInstance(myMonoScript.GetClass()) as MyCommonClass;

Base Class ScriptableObject:

MyCommonClass myCommonClass = ScriptableObject.CreateInstance(myMonoScript.GetClass()) as MyCommonClass;

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Answer 2

I know this is years later, but I wanted to leave a solution here for anyone that's struggled with this exact problem for hours on end. @dustingunn

NOTE: This is using ScriptableObject, and hasn't been tested with @aidesigner's suggestion of creating a Base Class System.Object.

Step 1 - Abstract class FTW

Declare an abstract class that inherits from ScriptableObject and include any methods you may need.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public abstract class CommonScriptableClass : ScriptableObject
 {
     public abstract void DoSomething();
 }

Step 2 - Subclass

Create a new script (or scripts) that you want to inherit from CommonScriptableClass and override any of its methods if applicable.

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

 public class TestClass : CommonScriptableClass
 {
     public override void DoSomething(){}
 }

Step 3 - Create SO from MonoScript

Now, in your custom Editor Window of choice:

 CommonScriptableObject newScript =
 (CommonScriptableObject)ScriptableObject.CreateInstance(monoScript.GetClass());
 newScript.DoSomething();
 Editor.CreateEditor(newScript).OnInspectorGUI();

Works in an Editor Window and displays correctly. Hope this helps someone.

How do you instantiate a script from a monoscript?

2 Replies

Step 1 - Abstract class FTW

Step 2 - Subclass

Step 3 - Create SO from MonoScript

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