fidgit_mixico.rb

require 'mixico'

module Redirector
  # @param [Object] target Target of the redirection.
  # @param [Array<Symbol>] methods ([]) If empty, redirect all methods, otherwise only redirect named ones.
  def self.create(target, *methods)
    my_module = Module.new
    
    if methods.empty?
      # Equivalent to gen_eval, but won't crash and probably lower performance.
      my_module.send :define_method, :method_missing do |method, *args, &block|
         target.send method, *args, &block
      end
    else
      # Just redirect named methods.
      methods.each do |method|
        my_module.send :define_method, method do |*args, &block|
          target.send method, *args, &block
        end
      end  
    end
        
    my_module
  end
end

class State  
  def initialize
    @state_packer = Packer.new
    self.extend @state_packer.redirector
    
    setup
  end
    
  # Set everything up at the start.
  def setup
    @header = "State:"
  
    label "chunky"
        
    @packer = pack do
      label "bacon"
      
      pack do
        @my_label = label "CHUNKY" # ivar on State, not a packer.
        label "BACON"
        @footer = "ended" # Check that outer var is set.
      end
    end    
  end
  
  # Dynamic additions later.
  def change    
    @packer.label "Cazoo!"
    @packer.pack do
      @header = "Changed State:" # Check that outer var is set.
      label "Cazoo too!"
    end
    
    @my_label.text = "VERY CHUNKY"
  end
  
  def draw
    puts @header
    @state_packer.draw
    puts @footer
  end
end

class Packer
  attr_reader :redirector
  
  def initialize
    @children = []
    @redirector = Redirector.create(self, :pack, :label, :inside)
  end
  
  def label(text)
    label = Label.new(text)
    add label
    
    label
  end
  
  def inside(&block)
    mix_eval(redirector, &block)    
  end
  
  def pack(&block)  
    packer = Packer.new
    @children << packer 
    
    context = eval('self', block.binding)
    context.mix_eval(packer.redirector, &block)    
      
    packer
  end
  
  def draw(indent = "")    
    puts "#{indent}--->"
    @children.each { |c| c.draw(indent + "  ") }
    puts "#{indent}<---"
  end
  
  protected
  def add(child)
    @children << child
  end
end

class Label
  attr_accessor :text
  
  def initialize(text)
    @text = text
  end
  
  def draw(indent)
    print indent
    puts @text
  end
end

state = State.new

state.draw
state.change

class Other
  def initialize(state)
    @state = state
  end
  
  def change
    @state.pack do
      pack do
        label "Added from another object"
      end
    end
  end
end

Other.new(state).change

state.pack do
  pack do
    label "Added from main"
  end
end

state.inside do
  label "Added from main using #inside"
end

puts
puts '--------'
puts

state.draw

=begin
State:
--->
  chunky
  --->
    bacon
    --->
      CHUNKY
      BACON
    <---
  <---
<---
ended

--------

Changed State:
--->
  chunky
  --->
    bacon
    --->
      VERY CHUNKY
      BACON
    <---
    Cazoo!
    --->
      Cazoo too!
    <---
  <---
  --->
    --->
      Added from another object
    <---
  <---
  --->
    --->
      Added from main
    <---
  <---
  Added from main using #inside
<---
ended
=end