DCI: Builder approach

dci-builder.rb

module RoleExtender

  def new properties = {}
    include_roles nil, properties
  end

  private

  def include_roles roles, properties
    instance = allocate()
    [roles].flatten.each do |r|
      instance.extend r
    end if roles
    instance.properties = properties if instance.respond_to? :properties=
    instance
  end
end

module ReaderRoleExtender

  include RoleExtender

  def as_json_reader props = {}
    include_roles JsonReaderRole, props
  end

  def as_csv_reader props = {}
    include_roles CsvReaderRole, props
  end
end

module JsonReaderRole
  def to_json
    #open file and format for json
    p "Json"
  end
end

module CsvReaderRole
  def to_csv
    #open file and format for csv
    p "Csv"
  end
end

class Reader
  class << self
    include ReaderRoleExtender
  end

  # regular includes
  [].each do |role|
    include role
  end

  attr_reader :file
  attr_reader :properties

  def properties= props
    @file = props.fetch(:file, "")
  end
end

jr = Reader.as_json_reader file: "/tmp/foo"
 => #<Reader:0x00000001e12a98 @options={:file=>"/tmp/foo"}> 
jr.to_json
"Json"
 => "Json" 
jr.to_csv
NoMethodError: undefined method 'to_csv' for #<Reader:0x00000001e12a98 @options={}>

cr = Reader.as_csv_reader file: "/tmp/foo"
 => #<Reader:0x00000001dff178 @options={:file=>"/tmp/foo"}> 
cr.to_csv
"Csv"
 => "Csv"