Getting an Entity from EntityType

[Turtledove 4]

So I need to create a lookup table of several of my custom entities, via the EntityType members of my entity registry. The entities are successfully registered;

 

    public static final EntityType<DemonFangEntity> DEMON_FANG = registerEntity(EntityType.Builder.create(DemonFangEntity::new, EntityClassification.MISC).size(0.7F, 0.7F), "demon_fang");

 

and when I need an entity to spawn I simply call the following method where I try to return an entity via a string key. In this case, I'd need this to return a DemonFangEntity object (it extends WithernautsMagicEntity):

 

    public WithernautsMagicEntity getMagicEntity(World worldIn, String key)
    {
        try {
            for (Field f : EntityRegistry.class.getDeclaredFields())
            {
                Object obj = f.get(null);
                if (obj instanceof EntityType)
                {
                    EntityType type = (EntityType)obj;
                    Entity entity = type.create(worldIn);
                    if (entity instanceof WithernautsMagicEntity)
                    {
                        WithernautsMagicEntity magicEntity = (WithernautsMagicEntity)entity;
                        if (magicEntity.getKey().equals(key))
                            return magicEntity;
                    }
                }
            }
            throw new IllegalArgumentException();
        } catch (IllegalAccessException e)
        {
            throw new RuntimeException(e);
        }
    }

 

However, this method currently throws an exception because Entity entity = type.create(worldIn) returns null. What's a way I could correctly return an object of EntityType's template type? Or is this just not possible without reflection?

 

Sidenote: I'm trying to do it this way because I don't want to create a giant conditional statement since it would not scale well at all with my project's scope.

Edited December 5, 2020 by Turtledove

[kiou.23 5]

Okay...

first thing wrong is with your reflection code: you are passing null into the .get() method, that's not how it works.

you need to pass it an instance of the Object that you got the Field from, in this case you need the instance of EntityRegistry.

 

But there's a way better way of accomplishing what you want, you can just get the Deffered Register from your EntityRegistry class, and it has a method called .getEntries(), I think it's pretty self explanatory what it does.

 

This should solve your problem and drastically simplify the code

[kiou.23 5]

1 hour ago, Turtledove said:

Sidenote: I'm trying to do it this way because I don't want to create a giant conditional statement since it would not scale well at all with my project's scope.

I don't see in which scenario not using reflection would result in a giant conditional statement

 

1 hour ago, Turtledove said:

and when I need an entity to spawn I simply call the following method where I try to return an entity via a string key.

Trying to get things by string is very error-prone, you should at a minimun store the Entity Id String in your EntityRegistry as a static final, and then use it when needed

[Turtledove 4]

30 minutes ago, kiou.23 said:

I don't see in which scenario not using reflection would result in a giant conditional statement

 

Trying to get things by string is very error-prone, you should at a minimun store the Entity Id String in your EntityRegistry as a static final, and then use it when needed

Ugly conditionals, as in:

switch key:
	case 'blah':
		return BlahEntity object
	case 'foo':
		return FooEntity object
	case 'bar':
		return BarEntity object
	.
	.
	.
	case 'blah':
		return BlahEntity object

Where I'd need to add to this whenever I add new relevant Entities. This is what I'm avoiding.

 

35 minutes ago, kiou.23 said:

Okay...

first thing wrong is with your reflection code: you are passing null into the .get() method, that's not how it works.

you need to pass it an instance of the Object that you got the Field from, in this case you need the instance of EntityRegistry.

 

This part works just fine, we pass null to field.get() in this case because the members it's looking for are static. It correctly retreives the EntityTypes, the problem is that I don't know how to get an Entity object out of it.

 

Edited December 5, 2020 by Turtledove

[TheGreyGhost 819]

Howdy

 

 

I'm not sure I understand the problem you're facing.

 

Because you control the creation of your own types, you should be able to create a map of the entity type and its string name when you create them, and when you get a string name, use that map to decide if it's one of your entities and then spawn it.  Your registered entity type has the factory in it already.

 

Using reflection to search your own registry class seems like a very strange idea to me.

 

I also suggest not to use static initialisers for your entity types; either used DeferredRegistry or use an event, like this

https://github.com/TheGreyGhost/MinecraftByExample/blob/master/src/main/java/minecraftbyexample/mbe81_entity_projectile/StartupCommon.java

 

Cheers

  TGG

 

 

 

 

 

[kiou.23 5]

22 minutes ago, Turtledove said:

It correctly retreives the EntityTypes, the problem is that I don't know how to get an Entity object out of it.

You can use EntityType.create(), this returns a new Entity

 

23 minutes ago, Turtledove said:

This part works just fine, we pass null to field.get() in this case because the members it's looking for are static.

Oh yeah, those are static, my bad. It's that I just spended the whole day doing reflection and getting non static values

[kiou.23 5]

27 minutes ago, Turtledove said:

Ugly conditionals, as in:

switch key:
	case 'blah':
		return BlahEntity object
	case 'foo':
		return FooEntity object
	case 'bar':
		return BarEntity object
	.
	.
	.
	case 'blah':
		return BlahEntity object

Where I'd need to add to this whenever I add new relevant Entities. This is what I'm avoiding.

Can't you make the method generic? make it receive a EntityType<T> and then return the entity from it

It also seems very redundant, why do you need a method for this, isn't it easier to call EntityRegistry.RANDOM_ENTITY_TYPE.get().create()?

 

I also don't get why you are using reflections. I suppose you're using Deferred Registries, and the Deferred Regsitry has a method that returns all entries. And if you're not using Deferred Registries, you should

Edited December 5, 2020 by kiou.23