c# - Unity: How to dynamically attach an unknown script to a GameObject (custom editor)

Question

I'm currently making a system for the Unity Editor (custom inspector and custom windows) that will automate and make things easier for the artists working on the game we're making, but I've hit a brick wall.

I'm trying to find a way to dynamically add, through an editor Textfield input and a GUI button, an unknown script to a gameobject in the scene. The artist/programmer will type the name of the script in the textfield and it will search and add to a gameobject, but I don't know how to proceed with this, specially since some functions of gameObject.AddComponent() are deprecated as of Unity 5.3

Here's what I tried to do:

public string scriptname;
GameObject obj = null;
scriptname = EditorGUILayout.TextField("Script name:", scriptname, GUILayout.MaxHeight(25));
if (GUILayout.Button("Attach script"))
{
    //search for the script to check if it exists, using DirectoryInfo
    DirectoryInfo dir = new DirectoryInfo(Application.dataPath);
    FileInfo[] info = dir.GetFiles("*.*", SearchOption.AllDirectories);
    foreach (FileInfo f in info) // cycles through all the files
    {
        if(f.Name == scriptname)
        {
            //attaches to the gameobject (NOT WORKING)
            System.Type MyScriptType = System.Type.GetType(scriptname + ",Assembly-CSharp"); 
            obj.AddComponent(MyScriptType);
        }
    }
}

(Of course, this is a summed up version, I copied the relevant lines from different parts of the script).

But it doesn't work. Any ideas?

Answer 1

After extensive experiment I was able get this. This covers all the Unity components too. Just made it an extension method to make life easier.

public static class ExtensionMethod
{
    public static Component AddComponentExt(this GameObject obj, string scriptName)
    {
        Component cmpnt = null;


        for (int i = 0; i < 10; i++)
        {
            //If call is null, make another call
            cmpnt = _AddComponentExt(obj, scriptName, i);

            //Exit if we are successful
            if (cmpnt != null)
            {
                break;
            }
        }


        //If still null then let user know an exception
        if (cmpnt == null)
        {
            Debug.LogError("Failed to Add Component");
            return null;
        }
        return cmpnt;
    }

    private static Component _AddComponentExt(GameObject obj, string className, int trials)
    {
        //Any script created by user(you)
        const string userMadeScript = "Assembly-CSharp, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null";
        //Any script/component that comes with Unity such as "Rigidbody"
        const string builtInScript = "UnityEngine, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null";

        //Any script/component that comes with Unity such as "Image"
        const string builtInScriptUI = "UnityEngine.UI, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null";

        //Any script/component that comes with Unity such as "Networking"
        const string builtInScriptNetwork = "UnityEngine.Networking, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null";

        //Any script/component that comes with Unity such as "AnalyticsTracker"
        const string builtInScriptAnalytics = "UnityEngine.Analytics, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null";

        //Any script/component that comes with Unity such as "AnalyticsTracker"
        const string builtInScriptHoloLens = "UnityEngine.HoloLens, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null";

        Assembly asm = null;

        try
        {
            //Decide if to get user script or built-in component
            switch (trials)
            {
                case 0:

                    asm = Assembly.Load(userMadeScript);
                    break;

                case 1:
                    //Get UnityEngine.Component Typical component format
                    className = "UnityEngine." + className;
                    asm = Assembly.Load(builtInScript);
                    break;
                case 2:
                    //Get UnityEngine.Component UI format
                    className = "UnityEngine.UI." + className;
                    asm = Assembly.Load(builtInScriptUI);
                    break;

                case 3:
                    //Get UnityEngine.Component Video format
                    className = "UnityEngine.Video." + className;
                    asm = Assembly.Load(builtInScript);
                    break;

                case 4:
                    //Get UnityEngine.Component Networking format
                    className = "UnityEngine.Networking." + className;
                    asm = Assembly.Load(builtInScriptNetwork);
                    break;
                case 5:
                    //Get UnityEngine.Component Analytics format
                    className = "UnityEngine.Analytics." + className;
                    asm = Assembly.Load(builtInScriptAnalytics);
                    break;

                case 6:
                    //Get UnityEngine.Component EventSystems format
                    className = "UnityEngine.EventSystems." + className;
                    asm = Assembly.Load(builtInScriptUI);
                    break;

                case 7:
                    //Get UnityEngine.Component Audio format
                    className = "UnityEngine.Audio." + className;
                    asm = Assembly.Load(builtInScriptHoloLens);
                    break;

                case 8:
                    //Get UnityEngine.Component SpatialMapping format
                    className = "UnityEngine.VR.WSA." + className;
                    asm = Assembly.Load(builtInScriptHoloLens);
                    break;

                case 9:
                    //Get UnityEngine.Component AI format
                    className = "UnityEngine.AI." + className;
                    asm = Assembly.Load(builtInScript);
                    break;
            }
        }
        catch (Exception e)
        {
            //Debug.Log("Failed to Load Assembly" + e.Message);
        }

        //Return if Assembly is null
        if (asm == null)
        {
            return null;
        }

        //Get type then return if it is null
        Type type = asm.GetType(className);
        if (type == null)
            return null;

        //Finally Add component since nothing is null
        Component cmpnt = obj.AddComponent(type);
        return cmpnt;
    }
}

Usage:

gameObject.AddComponentExt("YourScriptOrComponentName");

---

It is important to understand how I did it so that you can add support for new components in any future Unity updates.

For any script created by users:

1.Find out what needs to be in the ??? in the Assembly.Load function.

Assembly asm = Assembly.Load("???");

You can do that by putting this in your script:

Debug.Log("Info: " + this.GetType().Assembly);

I got: Assembly-CSharp, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null

We should now replace ??? with that.

Assembly asm = Assembly.Load("Assembly-CSharp, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null");

2.Find out what needs to be in the ??? in the asm.GetType function.

Assembly asm = Assembly.Load("Assembly-CSharp, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null");
Type type = asm.GetType(???); 

In this case, it is simply the name of the script you want to add to the GameObject.

Let's say that your script name is NathanScript:

Assembly asm = Assembly.Load("Assembly-CSharp, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null");
Type type = asm.GetType("NathanScript"); 
gameObject.AddComponent(type);

---

For Unity built in scripts/components scripts not created by users:

Example of this is the Rigidbody, Linerenderer, Image components. Just any component not created by the user.

1.Find out what needs to be in the ??? in the Assembly.Load function.

Assembly asm = Assembly.Load("???");

You can do that by putting this in your script:

ParticleSystem pt = gameObject.AddComponent<ParticleSystem>();
Debug.Log("Info11: " + pt.GetType().Assembly);

I got: UnityEngine, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null

We should now replace ??? with that.

Assembly asm = Assembly.Load("UnityEngine, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null");

2.Find out what needs to be in the ??? in the asm.GetType function.

Assembly asm = Assembly.Load("UnityEngine, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null");
Type type = asm.GetType(???); 

You can do that by putting this in your script:

ParticleSystem pt = gameObject.AddComponent<ParticleSystem>();
Debug.Log("Info: " + pt.GetType());

I got: UnityEngine.ParticleSystem

Remember that ParticleSystem is used as an example here. So the final string that will go to the asm.GetType function will be calculated like this:

string typeString = "UnityEngine." + componentName;

Let's say that the Component you want to add is LineRenderer:

Assembly asm = Assembly.Load("UnityEngine, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null");
string typeString = "UnityEngine." + "LineRenderer";
Type type = asm.GetType(typeString); 
gameObject.AddComponent(type);

---

Putting it together in an extension method:

As you can see, adding scripts you created and the script/components that comes with Unity requires totally different process. You can fix this by checking if the type if null. If the type is null, perform the other step. If the other step is null too then the script simply does not exit.