Espresso

_hidden.html.erb

<% filter.opts.each do |(k, v)| %>
  <input type="hidden" name="<%= k %>" value="<%= v %>" />
<% end %>

_select.html.erb

<select name="<%= filter.name %>">
	<option value="">-- Pick an issue</option>
	<% filter.collection.each do |item| %>
		<option value="<%= item.value %>"
  		<% if params[filter.name] == item.value.to_s %>
  		  selected="selected"
  		<% end %>
		>
		  <%= item.name %>
		</option>
	<% end %>
</select>

article_admin.rb

require 'ostruct'
class ArticleAdmin
  def columns
    [
      OpenStruct.new(value: :title.to_proc, name: "Title", link?: true, sort: :title),
      OpenStruct.new(value: :created_at.to_proc, name: "Created At", sort: :created_at),
      OpenStruct.new(value: ->(article) { article.issue.try(:name) }, name: "Issue", sort: :issue_id)
    ]
  end
end

article_filter.rb

class ArticleFilter < ModelFilter
  self.model = Article
  self.filter_classes = [
    BelongsToFilter.factory(:model_name => :issue, :pretty_attribute => :name)
  ]
end

articles_controller.rb

class ArticlesController < ApplicationController
  respond_to :html
  def index
    @model = ArticleAdmin.new
    @filter = ArticleFilter.new(params)
    @articles = @filter.collection.page(params[:page]).per(10)  
    respond_with @articles
  end
end

belongs_to_filter.rb

class BelongsToFilter
  class_attribute :model_name, :pretty_attribute
  
  def self.factory(opts={})
    Class.new(self).tap do |k|
      k.model_name = opts[:model_name]
      k.pretty_attribute = opts[:pretty_attribute]
    end
  end
  
  attr_accessor :opts
  def initialize(params)
    self.opts = {}
    self.opts[model_name] = params[model_name]
  end
  def call(query)
    query.where("#{model_name.to_s}_id" => self.opts[model_name]) if self.opts[model_name].present?
  end
  
  def type
    "select"
  end
  def name
    model_name
  end
  def collection
    model_name.to_s.camelize.constantize.all.map do |i|
      OpenStruct.new(
        :item =>i,
        :value => i.id,
        :name => i.send(pretty_attribute)
      )
    end
  end
end

index.html.erb

	<div id="topbar">
		<h1>Workflow</h1>
	</div>

	<div id="container">
	<div id="main">
	<div id="main_inner">

		<h1>Articles</h1>

  	<table class="table table-striped table-condensed">
  		<thead>
  		<tr>
  			<% @model.columns.each do |col| %>
  				<th><%= col.name %></th>
  			<% end %>
  		</tr>
  		</thead>
  		<% @articles.each do |article| %>
  			<tr>
  				<% @model.columns.each do |col| %>
  					<td>
    					<% if col.link? %><a href="<%= url_for article %>"><% end %>
    					<%= col.value.call(article) %>
    					<% if col.link? %></a><% end %>
  					</td>
  				<% end %>
  			</tr>
  		<% end %>
  	</table>
  	<%= paginate @articles %>

	</div>
	</div>

	<div id="left">
	<div id="left_inner">
		<h1>Navigation</h1>
	</div>
	</div>

	<div id="right">
	<div id="right_inner">
		<h1>Filter</h1>
		
		<%= request.query_parameters %>

		<h2>Issue</h2>

		<form>
			<% @filter.filters.each do |filter| %>
				<%= render :partial => filter.type, :locals => { :filter => filter } %>
			<% end %>
			<input type="hidden" name="sort" value="<%= params[:sort] %>" />
			<input type="submit" />
		</form>

		<h2>Sort</h2>
		<% @model.columns.each do |col| %>
			<p>
				<%= col.name %>:
				<%= link_to "Asc", @filter.sort("#{col.sort}:asc") %> | 
				<%= link_to "Desc", @filter.sort("#{col.sort}:desc") %>
			</p>
		<% end %>
	</div>
	</div>

	</div>

model_filter.rb

class ModelFilter
  class_attribute :model, :filter_classes
  attr_accessor :collection, :filters
  def initialize(params, initial_collection=Article.scoped)
    @filters = filter_classes.map { |k| k.new(params) }
    @filters.push SortFilter.new params
    @collection = @filters.inject(initial_collection) do |c, f|
      f.call(c) || c
    end
  end
  def sort(param)
    @filters.map(&:opts).inject(&:merge).merge(:sort => param)
  end
end

sort_filter.rb

class SortFilter
  attr_accessor :opts
  def initialize(params)
    self.opts = {}
    self.opts[:sort] = if params[:sort].present?
      params[:sort].gsub(":", " ")
    end
  end
  def type; "hidden"; end
  def call(query)
    query.order(opts[:sort]) if opts[:sort]
  end
end