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ASM : changing fields.


coolboy4531

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Learnt how to change methods in ASM, was worth it. lol

 

Now, I'm trying to learn how to change fields.

They're probably extremely similar, and probably easy to grab on to but I don't know where to learn :P

 

What I'm trying to do is lower the skeleton attack speed (I probably don't need to make a coremod, imo I don't know any alternatives)

 

Converting:

private EntityAIArrowAttack aiArrowAttack = new EntityAIArrowAttack(this, 1.0D, 20, 60, 15.0F);

to

private EntityAIArrowAttack aiArrowAttack = new EntityAIArrowAttack(this, 1.0D, 60, 60, 15.0F);

 

Any suggestions?

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Yep, made perfect sense :)

 

Although you can replace that field via reflection every time a skeleton is spawned (EntityJoinWorldEvent)

 

Yeah, I was leaning towards that, I learned a few things about Java reflection but not so deep into that.

If you can teach me a thing or two about how to replace that field, that would be greatful.

(You don't have to show me like noob codes, just need to get some advice xD)

 

If you would like to know how little I know about reflection I'll be happy to show what I know.

I know how to use "Field" to get the private value.

 

public class RandomClass {
private String s = "hi";
}

public class RandomClazz {

  public static void main(String[] args) throws Exception {
    RandomClass randClass = new RandomClass ();
    Field f = randClass.getClass().getDeclaredField("s");
    f.setAccessible(true);
    System.out.println(f.get(randClass));
  }
}

In my opinion, I don't even THINK this would work, because it was a long time ago that I learned this :P

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Okay, hold it.

 

I need you to restate that, because my brain - just too much work and stress happenin' right now xD.

 

So you are trying to tell me that the "instance" is the SRG name ("field_****")?

If so, would Forge automatically change that when the srg name is changed - to the actual value instead of field_**** to (e.g. getBlockName() )?

 

Also, how would I use it with the event?

 

@SubscribeEvent
public void onEntityJoinedWorld(EntityJoinWorldEvent event) {
if (event.entity instanceof EntitySkeleton) {
//what do I do here? 
//do I do --  Field.set(instance, value) -- ?
}
}

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Let me just suggest doing ASM anyway. It appears you already have experience with it, and the process is relatively simple if you just want to change 20 to 60.

 

The aiArrowAttack field is initialized in a hidden method called <init>, which is called before a new object is constructed. We can agree that the EntityAIArrowAttack will only appear once in this method, so we can use this as a reference point to find the integer constant we wish to change.

 

Iterate through the instructions in <init> and find a NEW instruction which has type 'EntityAIArrowAttack' (or obfuscated name respectively). Find the following instruction that is loading 20, and change it to 60.

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However, I really don't want to turn my mod into a coremod.

I prefer using Java reflection. :P

 

@diesieben:

I got 2 questions.

 

How would I change the field value?

new EntityAIArrowAttack(this, 1.0D, 60, 60, 15.0F);

 

For "getDeclaredField(String field)"

Do I use the SRG name (func_****, field_****) or compiled names (aiArrowAttack)?

I really couldn't understand what you were trying to tell me "both ways."

 

 

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However, I really don't want to turn my mod into a coremod.

I prefer using Java reflection. :P

 

@diesieben:

I got 2 questions.

 

How would I change the field value?

new EntityAIArrowAttack(this, 1.0D, 60, 60, 15.0F);

 

For "getDeclaredField(String field)"

Do I use the SRG name (func_****, field_****) or compiled names (aiArrowAttack)?

I really couldn't understand what you were trying to tell me "both ways."

In the decompiled workspace, the value has the name "aiArrowAttack". But if you recompile the code, the field is called field_****. So if you try to get the "aiArrowAttack" field in the decompiled workspace, it works, but not in the recompiled version, where it's called "field_****", so that field isn't there, with causes a exeption.

Don't PM me with questions. They will be ignored! Make a thread on the appropriate board for support.

 

1.12 -> 1.13 primer by williewillus.

 

1.7.10 and older versions of Minecraft are no longer supported due to it's age! Update to the latest version for support.

 

http://www.howoldisminecraft1710.today/

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There is a neat little class called ObfuscationReflectionHelper. Look at it.

Don't ask for support per PM! They'll get ignored! | If a post helped you, click the "Thank You" button at the top right corner of said post! |

mah twitter

This thread makes me sad because people just post copy-paste-ready code when it's obvious that the OP has little to no programming experience. This is not how learning works.

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