array_transformer.rb

gistfile1.txt

class Array
  
  def transform(new_array)
    delta = ArrayTransformer.new
    yield(delta)
    
    (self - new_array).each { |item| delta.call_remove(item) }
    (new_array - self).each { |item| delta.call_insert(item) }
    self
  end
  
end

class ArrayTransformer
  
  def insert(&block)
    @insert_method = block
  end
  
  def remove(&block)
    @remove_method = block
  end
  
  def call_insert(item)
    @insert_method[item] if @insert_method
  end
  
  def call_remove(item)
    @remove_method[item] if @remove_method
  end
  
end