Dapper

Dapper adds the ability to generate presenters for your rails project. Presenters are helpful with cleaning up your views. You can move any kind of logic out of your view and isolate it in a presenter.

Installation

Add this line to your application's Gemfile:

gem 'dapper'

And then execute:

$ bundle

Or install it yourself as:

$ gem install dapper

Usage

Once the gem is installed, run the presenters generator.

$ rails generate presenter CONTROLLER_NAME [actions]

Example:

$ rails generate presenter Albums index edit show

The result will be:

myrailsproject
  |~app/
    |~presenters/
      |~albums/
        |-edit_presenter.rb
        |-index_presenter.rb
        `-show_presenter.rb

Running the presenter generator without any actions will default to one index_presenter.rb

To take advantage of the presenter, instantiate it in your controller.

class AlbumsController < ApplicationController

  def edit
    album = Album.find(params[:id])
    @presenter = Albums::EditPresenter.new(album)
  end

  def index
    albums = Album.all
    @presenter = Albums::IndexPresenter.new(albums)
  end

  def show
    album = Album.find(params[:id])
    @presenter = Albums::ShowPresenter.new(album)
  end

end

The presenter has access to view templates and helpers. This makes is very easy to move ugly logic out of your views and put it in your presenters. Here is an example that is pulling some logic for getting the most recent photos from a photo album. Granted there are ways to better solve this in the model itself, but you get the idea. This type of logic is not uncommon in views. You could really put any type of display logic in a presenter. You can also combine multiple models in a presenter. The big benefit here is that using a presenter helps to maintain a flattened structure in your views.

module Albums
  class ShowPresenter < Dapper::Base
    def initialize(album)
      @album = album
    end

    def recent_photos
      unless album.photos.empty?
        album.photos(:photo_id => nil, :order => [:created_at.desc])[0..11].each do |photo|
          h.link_to( h.image_tag(photo.url_thumbnail), photo )
        end
      end
    end

  end
end

Presenters don't have to only make it easier to work with models. They can be used for any type of view logic. They could adjust the text of a button based on some environment conditions. That condition might have nothing to do with a model. You could also change the visibility of sections of your page. Anything really. This is the reason there is a presenter per view. Each view could have its own requirements for how it displays itself.

Acknowledgements

I wouldn't be doing justice to the open source community if I didn't give a big heads up to Jeff Casimir and his Draper project. It had much influence on the success of this project. It showed me how to do all the wiring into the Rails framework.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request