Add presenters pattern

[ldlsegovia]

Presenters

For generating presenters we use:

$ rails generate presenter users_show

This will create the UsersShowPresenter class, inheriting from a base class:

class UsersShowPresenter < PowerTypes::PresenterBase
end

And its corresponding rspec file:

require 'rails_helper'

describe UsersShowPresenter do
  pending "add some examples to (or delete) #{__FILE__}"
end

To initialize a presenter inside your controller action you should execute the present_with method with valid params:

class UsersController < InheritedResources::Base
  def show
    presenter_params = { param1: 1, param2: 2 }
    @presenter = present_with(:users_show, presenter_params)
  end
end

You can access view helper methods through the h method:

class UsersShowPresenter < PowerTypes::PresenterBase
  def platanus_link
    h.link_to "Hi Platanus!", "https://platan.us"
  end
end

You can access presenter_params inside the presenter as an attr_reader

class UsersController < InheritedResources::Base
  def show
    presenter_params = { platanus_url: "https://platan.us" }
    @presenter = present_with(:users_show, presenter_params)
  end
end

class UsersShowPresenter < PowerTypes::PresenterBase
  def platanus_link
    h.link_to "Hi Platanus!", platanus_url
  end
end

If the presenter param has a decorator, the attr_reader will be decorated.

class UsersController < InheritedResources::Base
  def show
    presenter_params = { user: user }
    @presenter = present_with(:users_show, presenter_params)
  end

  private

  def user
    @user ||= User.find!(params[:id])
  end
end

class UserDecorator < Draper::Decorator
  delegate_all

  def cool_view_name
    "~º#{name}º~"
  end
end

class UsersShowPresenter < PowerTypes::PresenterBase
  def platanus_link
    h.link_to "Hi #{user.cool_view_name}!", platanus_url
  end
end

In the view, you can use it like this:

<div><%= @presenter.platanus_link %></div>

[coveralls]

Coverage increased (+0.9%) to 96.899% when pulling 97c476b on presenters into 25b184e on master.