tapping Into Java with JRuby

Tapping into processing PVector class

I expect most rubyist know how to use tap to do some complex initialization in regular ruby, but probably fewer know that with JRuby you can also tap into a java class. PVector is class from vanilla processing (that I would prefer JRubyArt and propane users to ignore in favour of Vec2D and Vec3D ruby classes), however it is still possible to call PVector in JRubyArt and propane. See JRubyArt sketch and output below:-

attr_reader :pvec, :vec, :pvec2

def settings
  size 200, 200
end

def setup
  sketch_title 'Fred'
  @pvec = Java::ProcessingCore.PVector.new.tap do |v|
           v.x = 3
           v.y = 6
         end
  @vec = Vec2D.new(pvec) # this is possible via duck-typing
  # we need to know about both classes to do the reverse
  # first we return vec as an Array, then splat to produce 3 args
  @pvec2= Java::ProcessingCore.PVector.new(*(vec.to_a))
end

def draw
  p pvec
  puts pvec
  puts vec
  puts pvec2
  no_loop
end

A snapshot of running sketch

What this sketch demonstrates is that you can tap into a java class. It is possible via duck-typing to create (with no ceremony) a Vec2D instance from a PVector, it requires more ceremony but it is possible to create a PVector instance from Vec2D instance. For some reason PVector to String returns an array of java float.