C#•2y ago

❔ Unity3D C-Sharp Create class instance from Type

Hello need a little help trying to create an instance of a type at run time but once I try to create the instance it gets returned null, even after verifying that the time I'm looking for is correct but the System.Activator is not working for me I event tried to use the Assembly

35 Replies

OkashiKamiOP•2y ago

The function that does the conversion

  public static IEnumerable<object> GetClasses(Type type, string _namespace = null, Predicate<Type> predicate = null)
        {   
            var assembly = type.Assembly;
            var results = new List<Type>();
            IEnumerable<Type> types = assembly.GetTypes();
            if (!string.IsNullOrEmpty(_namespace))
                results.AddRange(types.Where(x => string.Equals(type.Namespace, _namespace, StringComparison.Ordinal)));
            results = results.Where(x => Equals(x.BaseType, type)).ToList();
            if (predicate != null)
                results = results.Where(t => predicate(t)).ToList();

            var classes = new List<object>();
            foreach (var result in results)
            {
                try
                {
                    var name = result.FullName;
                    var _class = Activator.CreateInstance(result, BindingFlags.Public);
                    if (_class != null)
                        classes.Add(_class);
                }
                catch(Exception ex)
                {
                    Debug.LogException(ex);
                }
            }

            return classes;
        }

  public static IEnumerable<object> GetClasses(Type type, string _namespace = null, Predicate<Type> predicate = null)
        {   
            var assembly = type.Assembly;
            var results = new List<Type>();
            IEnumerable<Type> types = assembly.GetTypes();
            if (!string.IsNullOrEmpty(_namespace))
                results.AddRange(types.Where(x => string.Equals(type.Namespace, _namespace, StringComparison.Ordinal)));
            results = results.Where(x => Equals(x.BaseType, type)).ToList();
            if (predicate != null)
                results = results.Where(t => predicate(t)).ToList();

            var classes = new List<object>();
            foreach (var result in results)
            {
                try
                {
                    var name = result.FullName;
                    var _class = Activator.CreateInstance(result, BindingFlags.Public);
                    if (_class != null)
                        classes.Add(_class);
                }
                catch(Exception ex)
                {
                    Debug.LogException(ex);
                }
            }

            return classes;
        }

OkashiKamiOP•2y ago

original Class

Modifier.cs

OkashiKamiOP•2y ago

Sub Classes

VoronoiModifier.cs

ChunckModifier.cs

MidpointDisplacement...

PerlinModifier.cs

SmoothModifier.cs

OkashiKamiOP•2y ago

The method that calls the function

 var classes = Utilities.GetClasses(typeof(Modifier), "OkashiKami.Terragen.Modifiers").ToList();
                foreach (var _class in classes)
                {
                    var name = _class.ToString().Split('.').Last();
                    if (name.Equals(nameof(ChunckModifier)))
                    {
                        if (self.me.modifiers.Find(x => x.GetType().Equals(typeof(ChunckModifier))) != null)
                        {
                            menu.AddDisabledItem(new GUIContent(name));
                            continue;
                        }
                    }

                    menu.AddItem(new GUIContent(name), false, ProcessDropDownButtonClick, _class);
                }

 var classes = Utilities.GetClasses(typeof(Modifier), "OkashiKami.Terragen.Modifiers").ToList();
                foreach (var _class in classes)
                {
                    var name = _class.ToString().Split('.').Last();
                    if (name.Equals(nameof(ChunckModifier)))
                    {
                        if (self.me.modifiers.Find(x => x.GetType().Equals(typeof(ChunckModifier))) != null)
                        {
                            menu.AddDisabledItem(new GUIContent(name));
                            continue;
                        }
                    }

                    menu.AddItem(new GUIContent(name), false, ProcessDropDownButtonClick, _class);
                }

mikernet•2y ago

Activator.CreateInstance does not return null (unless the type is Nullable<Something>) so something about how you are debugging things is not right. I'm not going to read through all that code but if you're saying that Activator.CreateInstance is returning null then I have my doubts about how you're testing this

OkashiKamiOP•2y ago

i event stepped through the code and everything is correct up to the section of the fist codebase right after var classes = new List<object>(); everything after that fails

mikernet•2y ago

everything after that fails

You need to be more specific about what that means Program crashes? You get an exception? You get a null when you don't expect a null?

OkashiKamiOP•2y ago

while stepping as soon as i get to the section that says Activator.createInstance it return null like i said not really sure i'm getting a MissingMethodException: Constructor on type 'OkashiKami.Terragen.Modifiers.SmoothModifier' not found. exception but all my classes have a default constructor in them so i really don't understand

mikernet•2y ago

OkashiKamiOP•2y ago

and i expect when i rand the Activator.CI to return an object of the type that was provided but instead i get a null value when after inspecting the elements with breakpoints all is good but not that part

mikernet•2y ago

Well if its throwing an exception then its not returning anything, including null, its throwing an exception That said...idk, it looks like you have a public default ctor So that doesnt make sense

OkashiKamiOP•2y ago

yes true one thing i did notice is that the exception doesn't get fired unless i put it in a try catch otherwise it doesn't do anything

mikernet•2y ago

You must have something weird going on because activator.createinstance has never had any problems afaik

OkashiKamiOP•2y ago

do you thing it's because those classes inherits a base class in my case Modifier.cs

mikernet•2y ago

No There is no overload of CreateInstance that takes 2 params with a second BindingFlags parameter So idk what overload that is calling But very likely not the right one Remove the binding flags parameter It's probably looking for a ctor that takes a BindingFlags parameter to pass that into Because it thinks youre trying to specify that as a ctor argument

mikernet•2y ago

This is probably the overload its calling: https://learn.microsoft.com/en-us/dotnet/api/system.activator.createinstance?view=net-7.0#system-activator-createinstance(system-type-system-object())

Activator.CreateInstance Method (System)

Creates an instance of the specified type using the constructor that best matches the specified parameters.

OkashiKamiOP•2y ago

so you know how on msdn they have CreateInstance(String, String) Creates an instance of the type whose name is specified, using the named assembly and parameterless constructor. for some reason that one is not available to me

mikernet•2y ago

Forget that You have a type All you need to do is call CreateInstance(type) Theres no reason for you to be using strings

OkashiKamiOP•2y ago

this is my Activator class looks like

mikernet•2y ago

Yes, and what I said stands

OkashiKamiOP•2y ago

let me try with just type

OkashiKamiOP•2y ago

here me stepping through the code

OkashiKamiOP•2y ago

i even show elements as we are stepping

mikernet•2y ago

It's not null If it was then it wouldnt be added to the list That 'null' value is something different

mikernet•2y ago

It's showing you properties on the object that are set:

OkashiKamiOP•2y ago

yeah it seams like it's creating and instance of the base class not the actual class of the type but what it inherits from

mikernet•2y ago

The 'null' is what ToString() is returning Which is probably coming from some base class I dont see a ToString() override on your classes so its probably coming from UnityObject Sorry UnityEngine.Object

mikernet•2y ago

OkashiKamiOP•2y ago

ah probably

mikernet•2y ago

Override ToString() on Modifier and return GetType().FullName And you'll see it'll show the class name Instead of 'null' The activation of the types is working fine

OkashiKamiOP•2y ago

your right ugh dam are you serious rn

mikernet•2y ago

🙂 Gotta love debugging rabbit holes 😛 We all get stuck in them sometimes

OkashiKamiOP•2y ago

i would of never guess thank you so much for your help very much appreciate it dam much love

Shirasho•2y ago

I've always wondered about that. 👍 The nullable type annotation never made sense.

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Unity3D C-Sharp Create class instance from Type