I am trying to use the Artemis entity system framework from JRuby. Here is the Java code that I am trying to convert to JRuby:
import com.artemis.Aspect;
import com.artemis.Component;
import com.artemis.Entity;
import com.artemis.World;
import com.artemis.systems.EntityProcessingSystem;
public class MyGame {
private World world;
public MyGame() {
world = new World();
Entity e = world.createEntity();
e.addComponent(new Position());
e.addToWorld();
world.setSystem(new ConsoleOutputSystem());
world.initialize();
for(int i = 0; i < 10; i++) {
world.setDelta(60);
world.process();
}
}
public static void main(String[] args) {
new MyGame();
}
}
class Position extends Component {
public int x;
public int y;
public Position() {
this.x = 0;
this.y = 0;
}
}
class ConsoleOutputSystem extends EntityProcessingSystem {
public ConsoleOutputSystem() {
super(Aspect.getAspectForAll(Position.class));
System.out.println("In system constructor");
}
@Override
protected void process(Entity entity) {
System.out.println("processing");
System.out.println(entity.getUuid());
}
}
When I execute this the output is:
In system constructor
processing
9e8a24a8-b778-4926-b305-5a426a2f0ce1
processing
...
The ConsoleOutputSystem.process() method gets called ten times. Here is my JRuby code:
require 'artemis.jar'
java_import com.artemis.Entity
java_import com.artemis.World
java_import com.artemis.Component
java_import com.artemis.Aspect
java_import com.artemis.systems.EntityProcessingSystem
class MyGame
attr_reader :world
def initialize
@world = World.new()
e = @world.create_entity()
e.add_component(Position.new())
e.add_to_world()
@world.set_system(ConsoleOutputSystem.new())
#@world.initialize
@world.java_send :initialize
10.times do
@world.set_delta(60)
@world.process()
end
end
end
class Position < Component
attr_accessor :x, :y
def initialize ()
@x = 0
@y = 0
end
end
class ConsoleOutputSystem < EntityProcessingSystem
def initialize()
puts 'in system constructor'
super(Aspect.get_aspect_for_all(Position))
end
java_signature 'protected void process(Entity)'
def process(entity)
puts 'process'
puts entity.getUuid
end
end
MyGame.new()
The output is:
in system constructor
So the ConsoleOutputSystem constructor gets called but not ConsoleOutputSystem.process(). I tried to use both @world.initialize and @world.java_send :initialize and the output is the same. Another thing I tried is to add java_signature 'protected void process(Entity)' to the ConsoleOutputSystem.process() method.
Several other classes from the Artemis package have protected methods named initialize() but I'm not sure if that is related to my issue.
[EDIT]
I've made some progress since I posted the question. @world.java_send :initialize works and the correct method is called. What doesn't work is Aspect.get_aspect_for_all(). In Java Aspect.getAspectForAll() expects
Class<? extends Component> , Class<? extends Component>[]
as arguments. In JRuby neither of these works as an argument to Aspect.getAspectForAll():
Position
Position.class
Position.java_class
Position.java_proxy_class
The only thing that worked was to create a Position instance upfront and pass its class to Aspect.getAspectForAll():
@position_class = Position.new().getClass()
Here is the code it works but it feels llike a kludge:
require 'artemis.jar'
java_import com.artemis.Entity
java_import com.artemis.World
java_import com.artemis.Component
java_import com.artemis.ComponentType
java_import com.artemis.ComponentMapper
java_import com.artemis.Aspect
java_import com.artemis.systems.EntityProcessingSystem
class MyGame
attr_reader :world
def initialize
@world = World.new()
e = @world.create_entity()
e.add_component(Position.new())
e.add_component(Velocity.new())
e.add_to_world()
@world.set_system(ConsoleOutputSystem.new(@world))
@world.java_send :initialize
5.times do
@world.set_delta(60)
@world.process
end
end
end
class Position < Component
attr_accessor :x, :y
def initialize ()
@x = rand(100)
@y = rand(100)
end
end
class Velocity < Component
attr_accessor :v
def initialize()
@v = 1.43
end
end
class ConsoleOutputSystem < EntityProcessingSystem
attr_accessor :position_class, :velocity_class
def initialize(world)
@position_class = Position.new().getClass()
@velocity_class = Velocity.new().getClass()
puts "@position_class: #{@position_class}"
puts "Position: #{Position}"
puts "Position.class: #{Position.class}"
puts "Position.java_class: #{Position.java_class}"
puts "Position.java_proxy_class: #{Position.java_proxy_class}"
super(Aspect.get_aspect_for_all(@position_class, @velocity_class))
end
def process(entity)
puts 'process'
puts entity.getUuid
position = entity.get_component(@position_class)
velocity = entity.get_component(@velocity_class)
position.x += 1
position.y += 1
velocity.v += 1
puts position.x
puts position.y
puts velocity.v
puts '----------'
end
end
game = MyGame.new()
The output of
puts "@position_class: #{@position_class}"
puts "Position: #{Position}"
puts "Position.class: #{Position.class}"
puts "Position.java_class: #{Position.java_class}"
puts "Position.java_proxy_class: #{Position.java_proxy_class}"
is:
@position_class: org.jruby.proxy.com.artemis.Component$Proxy0
Position: Position
Position.class: Class
Position.java_class: com.artemis.Component
Position.java_proxy_class: org.jruby.javasupport.proxy.JavaProxyClass
So, my problem is how to get to org.jruby.proxy.com.artemis.Component$Proxy0 without creating an instance of the Position class?
[EDIT 2]
Thanks to Namek's answer here is the code that works. It uses
@position_class = Position.java_proxy_class.java_class
@velocity_class = Velocity.java_proxy_class.java_class
so I don't need to create an instance of a JRuby class to get to its Java class:
require 'artemis.jar'
java_import com.artemis.Entity
java_import com.artemis.World
java_import com.artemis.Component
java_import com.artemis.ComponentType
java_import com.artemis.ComponentMapper
java_import com.artemis.Aspect
java_import com.artemis.systems.EntityProcessingSystem
class MyGame
attr_reader :world
def initialize
@world = World.new()
e = @world.create_entity()
e.add_component(Position.new())
e.add_component(Velocity.new())
e.add_to_world()
@world.set_system(ConsoleOutputSystem.new(@world))
@world.java_send :initialize
5.times do
@world.set_delta(60)
@world.process
end
end
end
class Position < Component
attr_accessor :x, :y
def initialize ()
@x = rand(100)
@y = rand(100)
end
end
class Velocity < Component
attr_accessor :v
def initialize()
@v = 1.43
end
end
class ConsoleOutputSystem < EntityProcessingSystem
attr_accessor :position_class, :velocity_class
def initialize(world)
@position_class = Position.java_proxy_class.java_class
@velocity_class = Velocity.java_proxy_class.java_class
super(Aspect.get_aspect_for_all(@position_class, @velocity_class))
end
def process(entity)
puts 'process'
puts entity.getUuid
position = entity.get_component(@position_class)
velocity = entity.get_component(@velocity_class)
position.x += 1
position.y += 1
velocity.v += 1
puts position.x
puts position.y
puts velocity.v
puts '----------'
end
end
game = MyGame.new()
Seems like your current problem is discussed here: http://jira.codehaus.org/browse/JRUBY-672
try to get your Java class like this: