NAME

dao

SYNOPSIS

a sa-weet-ass library for structuring rails applications using the 'data
access object' design pattern.  dao consists of two main data access
objects, *api* objects and *conducer* objects.  conducers combine the
presenter pattern with the conductor pattern.

API

  class Api < Dao::Api
    call('/posts') do
      get do
        data[:posts] = Post.all.map{|post| post.attributes}
      end

      post do
        post = Post.new(params[:post])

        if post.save
          data[:post] = post.attributes
        else
          status 420
        end
      end
    end
  end

CONDUCER

  # TODO

wikipedia has this to say about dao in general

  "

    In computer software, a data access object (DAO) is an object that
    provides an abstract interface to some type of database or persistence
    mechanism, providing some specific operations without exposing details
    of the database.  It provides a mapping from application calls to the
    persistence layer. This isolation separates the concerns of what data
    accesses the application needs, in terms of domain-specific objects and
    data types (the public interface of the DAO), and how these needs can be
    satisfied with a specific DBMS, database schema, etc. (the
    implementation of the DAO).

  " 
    - http://en.wikipedia.org/wiki/Data_access_object

and

  "
    Models are not data access objects...
  "

    - http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller

DESCRITPION

API
  applications that are written on dao look like this in ruby

    result = api.call('/posts/new', params)

  and like this in javascript

    result = api.call('/posts/new', params)

  in command-line applications they look like this

    result = api.call('/posts/new', params)

  and in tests this syntax is used

    result = api.call('/posts/new', params)

  when a developer wants to understand the interface of a dao application
  she does this

    vi app/api.rb

  when a developer of a dao application wants to play with a dao application
  interactively she does

    (rails console)

    > api = Api.new result = api.call('/posts/new', params)

  when a remote client wants to understand the api of a dao application she
  does

    curl --silent http://dao.app.com/api | less

  this kind of brutally consistent interface is made possible by structuring
  access to data around the finest data structure of all time - the hash.
  in the case of dao the hash is a well structured and slightly clever hash,
  but a simple hash interface is the basis of every bit of goodness dao has
  to offer.

  in dao, application developers do not bring models into controllers and,
  especially not into views.  instead, a unified interface to application
  logic and data is used everywhere: in tests, in controllers, from the
  command-line, and also from javascript.

  this seperation of concerns brings with it many, many desirable qualities:

    - total seperation of concerns between the front and back end of a web
      application.  when developers are using dao changes to the data model
      have zero effect on controllers and views.

    - issues related to having models in controllers and views such as
      difficulty reasoning about caching and n+1 queries in views killing
      the db simply disappear.

    - bad programming practices like using quasi-global variables
      (current_user) or decorating models with view specific attributes
      (password_verification) are no longer needed.

    - developers are able to reason over the abilities of an application by
      reading only a few source files.

    - databases can be swapped, mixed, or alternate storage/caching
      mechanisms added at any time without affecting the application's
      controllers or views.

    - transition from form based views to semi-ajax ones to fully-ajax ones
      is direct.

    - forms and interfaces that involve dozens of models are as easy to deal
      with as simple ones.

    - code can be optimized at the interface

READING

http://blog.plataformatec.com.br/2012/03/barebone-models-to-use-with-actionpack-in-rails-4-0/
http://martinfowler.com/eaaCatalog/serviceLayer.html
http://blog.firsthand.ca/2011/10/rails-is-not-your-application.html
http://best-practice-software-engineering.ifs.tuwien.ac.at/patterns/dao.html
http://www.codefutures.com/data-access-object/
http://java.sun.com/blueprints/corej2eepatterns/Patterns/DataAccessObject.html
http://www.paperplanes.de/2010/5/7/activerecord_callbacks_ruined_my_life.html
http://google-styleguide.googlecode.com/svn/trunk/jsoncstyleguide.xml
http://pragdave.blogs.pragprog.com/pragdave/2007/03/the_radar_archi.html
http://borisstaal.com/post/22586260753/mvc-in-a-browser-vs-reality

INSTALL

gem 'dao', :path => File.expand_path('..') ### Gemfile
rails generate dao api
vim -o app/api.rb app/controllers/api_controller.rb
curl --silent http://0.0.0.0:3000/api
curl --silent http://0.0.0.0:3000/api/ping

HISTORY

4.0.0
  - dao depends has tied itself to rails, for better or worse...
  - drop custom form encoding.  just use a rack-like approach.
  - dao form parameter encoding has changed slightly to 'dao[/api/path][x,y,z]=42'
  - dao form paramters are now preparsed in a before filter