ArchPresenter

ArchPresenter is a simple, lightweight gem that implements the Presenter pattern.

It allows you to slim down your models and controllers by extracting the logic related to class presentation. You can learn more about this pattern on the Jay Fields' blog.

Installation

Add this line to your application's Gemfile:

gem 'arch_presenter'

And then run:

$ bundle

Usage

Super-quick example

Simple, skinny model:

# app/models/user.rb
class User
  def first_name
    'John'
  end
  def last_name
    'Smith'
  end
  def title
    'Mr.'
  end
  def name_visible?
    true
  end
end

Presentation logic moved to the presenter:

# app/presenters/user_presenter.rb
class UserPresenter < ArchPresenter::Base
  def display_name
    if name_visible? 
      [title, first_name, last_name].join(' ')
    else
      '(Name hidden)'
    end
  end
end

Presenting the object in the controller:

# app/controllers/users_cotroller.rb
class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
    @user = present(@user)
  end
end

Using the display_name function:

# app/views/users/show.html.erb
<h1><%=@user.display_name %> - User profile</h1>

Creating presenter classes

First you will need to create a class that will be used to decorate your object.

Presenter class files should be placed in app/presenters/ and should inherit from ArchPresenter::Base.

Autoloading

You might wish to add app/presenters/ to your autoload path. This will allow rails to automatically detect changes made to the presenter files without the need to restart the server.

In config/application.rb add:

config.autoload_paths << Rails.root.join('app', 'presenters')

Decorating

ArchPresenter gem provides a #present function that can be invoked in your controller (or in your view if you preffer decorating your classes there).

To decorate your class use the #present function.

In the controller:

user = User.find(1)
@user = present(user)

or in the view:

<body>
<% @user = present(@user) %>
Hello <%= @user.full_name %>!
</body>

Mini-tutorial

We have a user model that looks like this:

# app/models/user.rb
class User < ActiveRecord::Base
  def first_name
    'John'
  end
  def last_name
    'Smith'
  end
  def title
    'Mr.'
  end
  def name_visible?
    true
  end
  def display_name
    if name_visible? 
      [title, first_name, last_name].join(' ')
    else
      '(Name hidden)'
    end
  end
end

where first_name, last_name and title are user table cloumns and display_name is only used to show the name while displaying information about the user. display_name doesn't really belong to the model and we want to move it to a separate class - the presenter.

We create a new file in app/presenters and move the display_name there:

class UserPresenter < ActiveRecord::Base
  def display_name
    if name_visible? 
      [title, first_name, last_name].join(' ')
    else
      '(Name hidden)'
    end
  end
end

Now in our controller we can use the present method:

# app/controllers/users_cotroller.rb
class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
    @user = present(@user)
  end
end

This will add the display_name method to our @user. We can now use it in the view:

# app/views/users/show.html.erb
<h1><%=@user.display_name %> - User profile</h1>

Contributing

Fork it ( https://github.com/[my-github-username]/arch_presenter/fork )
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create a new Pull Request

arch_presenter

Development