dci_view.rb

require 'alias_dci'

class Article < Struct.new(:subject,:body);end

class TextView 
  attr_reader :contents
  def initialize
    @contents = ""
  end
end

class GenerateAppendView
  include AliasDCI::Context

  role :displayable_article do
    def summary
      "#{subject} : #{body}"
    end
  end

  role :canvas do
    def render
      @contents << " << " unless @contents.empty?
      @contents << "#{displayable_article.summary}"
    end
  end
  
  def initialize(article, view)
    rebind(article, view)
  end

  def rebind(article, view)
    assign_named_roles(:displayable_article => article, :canvas => view, :force => true)
  end

  def render
    in_context do
      canvas.render
    end
  end
  
end

article = Article.new("Hi there...", "I like turtles!")
text_view = TextView.new
view_context  = GenerateAppendView.new(article,text_view)

view_context.render
text_view.contents # => "Hi there... : I like turtles!"
puts text_view.contents

article.subject = "And Now I Say ..GoodBye"
article.body = "Cyas..."

view_context.render
text_view.contents # => "Hi there... : I like turtles! << And Now I Say ..GoodBye : Cyas..."
puts text_view.contents


# >> Hi there... : I like turtles!
# >> Hi there... : I like turtles! << And Now I Say ..GoodBye : Cyas...