How do i make a list of generic classes?

Question

First of all, I want mods in my game, as stated in a previous question, I want to do that via registries. Users make content known to the game in the form of 'Registering' it, then it can be used in several other stuff. Registering a block to have it appear on the terrain is one example.

Registering is done in the form of events, where each registry has an OnEntryCollection event with a list where other classes subscribe to in order to add Entries, and then it gets invoked to gather said entries.

Basically I have a registry system, where there's a large meta-registry(The Game-registry) that has a list of smaller Registry<T> registries, each dedicated to a type (a block, an item, etc). I want to be able to add to these registries via a Registry.Add(T obj) method, but I'm not exactly sure how to do that because in order to store them I had to use an empty interface I made (IRegistry).

This is meant to be a way for me to add Entries in through code, from specific files I parse in, while also allowing modders to add in custom content through registry events I will add later. Nothing is meant to be added in through the inspector, rather registered in through events.

My code:

Game-Registry:

[SerializeField] List<IRegistry> registries = new List<IRegistry>();

Registry :

public class Registry<T> : IRegistry where T : IRegistryEntry {
    Dictionary<ResourceLocation, T> EntryDictionary = new Dictionary<ResourceLocation, T>();

    public delegate void registryAdditionHandler(List<T> entries);
    public event registryAdditionHandler OnRegisterAddEntries;

    ResourceLocation keyName;

    public Registry(ResourceLocation keyName) {
        this.keyName = keyName;
    }

    public void Register(T entry) {
        EntryDictionary.Add(entry.GetRegistryName(), entry);
    }
    public void Remove(ResourceLocation loc) {
        EntryDictionary.Remove(loc);
    }

    public T Get(ResourceLocation key) {
       return EntryDictionary[key];
    }
    public int Count() {
        return EntryDictionary.Count;

    }

    public bool ContainsEntryKey(ResourceLocation key) {
        return EntryDictionary.ContainsKey(key);
    }
    public bool ContainsEntryValue(T value) {
        return EntryDictionary.ContainsValue(value);
    }

    public bool TryGetValue(ResourceLocation key, out T value) {
        if (EntryDictionary.TryGetValue(key,out value)) {
            return true;
        }
        return false;
    }

    public ResourceLocation getRegistryName() {
        return keyName;
    }
}

IRegistry interface:

public interface IRegistry  {
}

Answer 1

Are you looking for something like this?

public class MetaRegistry
{
    Dictionary<System.Type, IRegistry> _registries;

    Registry<T> GetOrCreateRegistryOfType<T>() where T: IRegistryEntry {
        Registry<T> registry;
        if (_registries.TryGetValue(typeof(T), out IRegistry interfaceRegistry)) {
            registry = (Registry<T>)interfaceRegistry;
        } else {
            registry = new Registry<T>();
            _registries.Add(typeof(T), registry);
        }
        return registry;
    }

    void AddToRegistry<T>(T value) where T : IRegistryEntry {
        GetOrCreateRegistryOfType<T>().Add(value);
    }
}