Using json in ruby-processing

It is actually far easier to use rubys json library than processing/java, because all you need is a hash to convert to_json, and vice versa. Here is one of Daniel Shiffmans sketches given the ruby-processing treatment. It might be also possible to do something similar with XML using Nokogiri (ruby hash to XML) and rails supports (XML to ruby hash).

require "json"

attr_reader :bubbles, :bubble_data

def setup()
  size(640, 360)
  # read source_string from file
  load_data
end

def draw
  background 255
  bubbles.each do|bubble|
    bubble.display
    bubble.rollover(mouse_x, mouse_y)
  end
end

def load_data
  source_string = open("data/data.json", "r").read
  # parse the source string
  @bubble_data = BubbleData.new

  # get the bubble_data from the top level hash
  data = bubble_data.extract_data source_string
  @bubbles = []
  # iterate the bubble_data array, and create an array of bubbles
  data.each do |point|
    bubbles << Bubble.new(
      point["position"]["x"],
      point["position"]["y"],
      point["diameter"],
      point["label"])
  end
end

def save_data
  # demonstrate how easy it is to create json object from a hash in ruby
  # json = bubble_data.to_hash.to_json # if you don't require pretty output
  json = JSON.pretty_generate(bubble_data.to_hash) # pretty output
  # overwite existing 'data.json' 
  open("data/data.json", 'w') {|f| f.write(json) }
end

def mouse_pressed
  # create a new bubble instance, where mouse was clicked
  @bubble_data.add_bubble(Bubble.new(mouse_x, mouse_y, rand(40 .. 80), "new label"))
  save_data
  # reload the json data from the freshly created file
  load_data
end

class BubbleData
  attr_reader :name, :data
  def initialize name = "bubbles"
    @name = name
    @data = []
  end

  def add_bubble bubble
    data << bubble
  end

  def extract_data source_string
    @data = JSON.parse(source_string)[name]
  end

  def to_hash
    {name => data.map{|point| point.to_hash}}
  end

end

class Bubble
  attr_reader :x, :y, :diameter, :name, :over

  def initialize(x, y, diameter, name)
    @x, @y, @diameter, @name = x, y, diameter, name
    @over = false
  end

  def rollover px, py
    d = dist px, py, x, y
    @over = (d < diameter / 2.0)
  end

  def display
    stroke 0
    stroke_weight 2
    no_fill
    ellipse x, y, diameter, diameter
    if over
      fill 0
      text_align CENTER
      text(name, x, y + diameter / 2.0 + 20)
    end
  end

  def to_hash
    {"position" => {"x" => x, "y" => y}, "diameter" => diameter, "label" => name}
  end
end

The data "data.json"

{
  "bubbles": [
      {
        "position": {
          "x": 160,
          "y": 103
        },
        "diameter": 43.19838,
        "label": "Happy"
      },
      {
        "position": {
          "x": 372,
          "y": 137
        },
        "diameter": 52.42526,
        "label": "Sad"
      },
      {
        "position": {
          "x": 273,
          "y": 235
        },
        "diameter": 61.14072,
        "label": "Joyous"
      },
      {
        "position": {
          "x": 121,
          "y": 179
        },
        "diameter": 44.758068,
        "label": "Melancholy"
      }
    ]
}