gistfile1.rb

# * I think some attr should be filtered by controllers,
#   while others by models (ie. computed values, as counter_cache)
# * Casting http params should not be the model direct responsibility ("1" => true, urg)
# * Using multiple controllers for a same model would be more convenient
# * I would love controllers to be more declarative

class Comment < ActiveRecord::Base
  belongs_to :user # user_id (integer)
  belongs_to :post # post_id (integer)
  # title (string)
  # content (text)
  # created_at, updated_at (datetime)
end

class CommentsController < ApplicationController
  # It's a "sugar" example, the same should be attainable with a inheriting class to be more
  # specialised and/or modular
  params_for :comment, allow: [:title, :content] do |p|
    p.title { |value| value.strip } # I prefer stripping in the model, but this is for demonstration
    strip :title, :content # Declarative alternative, custom methods for common patterns

    p.post_id { params[:post_id] } # Because in a nested resource
  end

  def create
    # Default behaviour is the same, so it can be DRYed easily (responders)
    @comment = current_user.comments.create(params[:comment])
    ...
    # Or maybe use a special method
    @comment = current_user.comments.create(params_for(:comment))
  end
end

# Need to think through:
# * Mass assignments over relations
# * Specialisation depending on actions and/or roles
# * Inheritance behaviour
# * Also share some validations controller side?