I am trying to create a Vector class for use with LuaJ. The end goal is to have the user not write much lua, and have most of the work done on my Java engine.
As my understanding goes, I need to set the metatable for the lua representation of my Java vector class? The problem I am having though, is that when I am trying to overwrite some metatable functionality it doesn't seem to have any affect in my lua script. What I am trying to do now is overwrite the + operator, so I can add two vectors together or add a vector by a constant.
Here is my Vector class so far:
package math;
import org.luaj.vm2.*;
import org.luaj.vm2.lib.*;
import org.luaj.vm2.lib.jse.*;
public class Vector3Lua {
public float X;
public float Y;
public float Z;
public Vector3Lua unit;
static {
// Setup Vector class
LuaValue vectorClass = CoerceJavaToLua.coerce(Vector3Lua.class);
// Metatable stuff
LuaTable t = new LuaTable();
t.set("__add", new TwoArgFunction() {
public LuaValue call(LuaValue x, LuaValue y) {
System.out.println("TEST1: " + x);
System.out.println("TEST2: " + y);
return x;
}
});
t.set("__index", t);
vectorClass.setmetatable(t);
// Bind "Vector3" to our class
luaj.globals.set("Vector3", vectorClass);
}
public Vector3Lua() {
// Empty
}
// Java constructor
public Vector3Lua(float X, float Y, float Z) {
this.X = X;
this.Y = Y;
this.Z = Z;
this.unit = new Vector3Lua(); // TODO Make this automatically calculate
System.out.println("HELLO");
}
// Lua constructor
static public class New extends ThreeArgFunction {
@Override
public LuaValue call(LuaValue arg0, LuaValue arg1, LuaValue arg2) {
return CoerceJavaToLua.coerce(new Vector3Lua(arg0.tofloat(), arg1.tofloat(), arg2.tofloat()));
}
}
// Lua Function - Dot Product
public float Dot(Vector3Lua other) {
if ( other == null ) {
return 0;
}
return X * other.X + Y * other.Y + Z * other.Z;
}
// Lua Function - Cross Product
public LuaValue Cross(Vector3Lua other) {
Vector3Lua result = new Vector3Lua( Y * other.Z - Z * other.Y,
Z * other.X - X * other.Z,
X * other.Y - Y * other.X );
return CoerceJavaToLua.coerce(result);
}
}Here is the lua script that makes use of this:
local test1 = Vector3.new(2, 3, 4);
local test2 = Vector3.new(1, 2, 3);
print(test1);
print(test2);
print(test1+2); The last line produces an error, as it says I cannot add a userdata and a number together. However, in my vector class I tried to get it to just print what is being added, and just return the original data (to test). So I believe my problem is how I am defining my metatable; In my vector class, the two print's are never called.
