[SOLVED] [1.10.2] Detect if a biome is a specific type of forest

[Daeruin]

In my world generator class I have been using World#getBiomeGenForCoords to get the current biome and check if it's a forest biome. However, I realized I need to detect which TYPE of forest it is (NORMAL, BIRCH, FLOWER ROOFED). I can see that BiomeForest has a Type enum, but I'm not sure how to access that value given that the current biome may or may not even be of the BiomeForest type. Does that make sense?

[Choonster]

Did you try looking at the

BiomeForest

class? There's a field called

type

that stores the

BiomeForest.Type

value.

 

There's no public getter method, so you'll need to access it with reflection.

 

If you don't know whether a

Biome

is a

BiomeForest

, check with

instanceof

.

[Daeruin]

Thanks for your reply. I am already using instanceof to determine if the biome is a BiomeForest, so I'm good there. And yes, I looked at the BiomeForest class and saw the type field. I just didn't know how to access it.

 

I've never used reflection, so I guess I have more reading to do. If there's a particularly good resource you can point me to online, I'd me much obliged. Unless someone has a quick explanation of how I can use it in this case.

[Draco18s]

Use the ReflectionHelper class.  You'll need to know both the MCP name and the SRG name though.

You'll have to use MCPBot to get the SRG name.

[Choonster]

Jabelar has a brief explanation of reflection here.

 

What he doesn't explain there is that each vanilla method/field has multiple names depending on the environment and that you need to check for these when accessing them via reflection.

 

There are three types of names:

• Notch - Fully Obfuscated - These are the names produced by Mojang's obfuscation process, the vanilla JARs use these names. They change with each Minecraft version. They're usually a few letters long, e.g.

  a

  ,

  bb

  or

  ff

  .
  

• SRG/Searge - Semi-obfuscated - These are auto-generated by MCP and FML deobfuscates to them at runtime outside of the development environment. ForgeGradle reobfuscates your code to these names when you run the

  build

  task. They remain stable between Minecraft versions. Examples include

  func_110121_a

  (a method),

  field_110285_bP

  (a field) and

  p_110121_0_

  (a parameter).
  

• MCP - Deobfuscated - These are contributed by the community using MCPBot. They're the names you see in the development environment. Examples include

  isNullOrEmpty

  (

  func_110121_a

  ),

  gallopTime

  (

  field_110285_bP

  ) and

  str

  (

  p_110121_0_

  ).

 

Instead of using

Class#getDeclaredField

or

Class#getDeclaredMethod

, use

ReflectionHelper.findField

or

ReflectionHelper.findMethod

to get the

Field

/

Method

object before unreflecting it into a

MethodHandle

(as Jabelar explains). You need to pass both the MCP and SRG names when accessing a vanilla field/method.

 

I have a class that does this here. You can see it in use here, here, here and here.

[Daeruin]

Thank you kindly, good sirs. I'll read up on all that tomorrow. Hopefully it goes well.

 

One thing, though. I noticed that the type field in BiomeForest is private final. Seems like that will block access to the field's value. Am I right? Or will reflection let me overcome that?

[Choonster]

Thank you kindly, good sirs. I'll read up on all that tomorrow. Hopefully it goes well.

 

One thing, though. I noticed that the type field in BiomeForest is private final. Seems like that will block access to the field's value. Am I right? Or will reflection let me overcome that?

 

final

means the field is read-only, i.e. you can get its value but you can't set a new value. There are ways around this (see

FinalFieldHelper

and

EnumHelper

), but you generally shouldn't do this unless it's absolutely necessary.

[Choonster]

There is no need to convert things into a MethodHandle unless you really need the utmost performance, which you rarely do. First measure that you actually have a performance problem with reflection.

 

Is there any downside to using

MethodHandle

s instead of

Method

s/

Field

s?

[Daeruin]

final

means the field is read-only, i.e. you can get its value but you can't set a new value. There are ways around this (see

FinalFieldHelper

and

EnumHelper

), but you generally shouldn't do this unless it's absolutely necessary.

That's fine. I only need to read the value to find out what kind of biome it is. I was more concerned about it being private.

 

Edit: Now that I've done more reading, I see that it is indeed possible to access private fields with reflection.

[Draco18s]

Edit: Now that I've done more reading, I see that it is indeed possible to access private fields with reflection.

 

That's why it was suggested that you use reflection, because reflection can do that.

[Daeruin]

It seems to be working now. I didn't use MethodHandles, and performance seems to be OK. Thanks for posting the links to your example mod, Choonster; the examples were nice. I didn't find jabelar's info to be very helpful, but there was a link to a page that was super helpful:

 

http://tutorials.jenkov.com/java-reflection/index.html

 

It took me a minute to figure out how to use the MCPbot (http://mcpbot.bspk.rs/help). I discovered that there's yet another type of forest which is a subclass of BiomeForest that I had to account for. Here's the completed code from my world generator class, in case it helps anyone later. I'd be glad for feedback as well.

 

Biome biome = world.getBiomeGenForCoords(pos);
boolean rightForestType = false;

if (biome instanceof BiomeForest && !(biome instanceof BiomeForestMutated))
{
try
{
	Class<?> biomeClass = biome.getClass();
	Field typeField = ReflectionHelper.findField(biomeClass, "type", "field_150632_aF");
	Object biomeType = typeField.get(biome);
	if (biomeType == BiomeForest.Type.NORMAL)
		rightForestType = true;
}
catch (IllegalAccessException x)
{
	x.printStackTrace();
	throw new ReflectionHelper.UnableToAccessFieldException(null, x);
}

if (rightForestType == true) { DO STUFF }

[Daeruin]

Ohhh, I see. I can get the field up front, because I know which class it's coming from. I don't even need to get the class itself, as long as I'm making sure to get the field value only when the biome being generated is of the right type.

 

New code:

 

public class PrimalWorldGen implements IWorldGenerator
{
static final Field typeField = ReflectionHelper.findField(BiomeForest.class, "type", "field_150632_aF");

...

private void generateTrees(WorldGenerator generator, World world, Random rand, int chunk_X, int chunk_Z, int chancesToSpawn)
{
	Biome biome = world.getBiome(pos);
	boolean rightForestType = false;

	if (biome instanceof BiomeForest && !(biome instanceof BiomeForestMutated))
	{
		try
		{
			Object biomeType = typeField.get(biome);
			if (biomeType == BiomeForest.Type.NORMAL)
				rightForestType = true;
		}
		catch (IllegalAccessException x)
		{
			x.printStackTrace();
			throw new ReflectionHelper.UnableToAccessFieldException(null, x);
		}

		if (rightForestType == true) { DO STUFF }
	}
}