DataWatchers - saving and retrieving float values

[Tomalla]

Hi there. I've been recently fiddling around with Entities and DataWatchers. I've added a new entity which is a block with settable width, height and length. The entities have the first two already implemented so I had to add length field which is a float variable. I'm using DataWatcher to synch this field with the same entity on the client side.

 

I'm surprised there's no methods in DataWatcher to actually retrieve a float value! The permitted Object classes are: Byte, Short, Integer, Float, String, ItemStack and ChunkCoordinates, as listed in DataWatcher.java at the end of the file. However only methods for retrieving Byte, Short, Integer, String and ItemStack values are provided, which is ridiculous. Here's an example of such a method:

 

    public short getWatchableObjectShort(int par1)
    {
        return ((Short)this.getWatchedObject(par1).getObject()).shortValue();
    }

 

It's easy to make another method by analogy for retrieving float values, but there's one problem: DataWatcher.getWatchedObject(int) method is private - it can be accessed only from within the DataWatcher class itself.

 

Solutions? I could either use Integer for storing a float value ( i.e. value 5.3F would be stored as int value of 530, 12.56F as 1256 and so on ) - this field is not supposed no be big so it should work, however it's not a method for all of the applications obviously. Or ... modify the DataWatcher class, which I'd like to avoid doing.

 

Thoughts? Am I doing something wrong or am I missing something completely?

[mnn]

it's your entity, you can modify its datawatcher's getWatchedObject flags to be public in entity constructor. but invoking method via reflection won't be cheap . using transformer in this case seems a bit like overkill, I'd go with that custom fixed point decimal type.

 

PS: I was wrong, invoking method via reflection is actually (after some time) same as doing it the native way . http://stackoverflow.com/a/414823/1017211

[Tomalla]

Holy mother ... I've spent too much time programming in C++. It's like ... a sorcery of sort, changing class members accessors on the fly? I had no idea it's even possible. Java is full of surprises I see.

 

It seems it works, but I'd appreciate if you actually took a look at this code and see if there's nothing more to modify in it:

 

http://paste.minecraftforge.net/view/ed9c5d02

 

Thanks for telling me about these ... how are they called? Reflections?

 

Cheers!

[mnn]

yep, reflection. when I first saw that in C# I was quite stunned . For performance reasons I'd done setting access stuff only after datawatcher creation (in contructor of your entity?) and also the Method instance could be cached in your entity. But I might be wrong, don't have many experience with Java reflection. (But on the other hand, those changes shouldn't break anything.)