PresentFoo

PresentFoo is meant to be a very lightweight presenter library for Rails. Presenters are a great way to move logic out of views and controllers into a class which represents the state of a "view" whether that be HTML, JSON, or other. It's also a way to reduce the junk-drawer effect that happens in the /helpers directory of many large Rails applications. This is a super basic implementation and I hope to grow it over time. If you have thoughts on things that would be helpful I'd love the feedback.

Installation

Add this line to your application's Gemfile:

gem 'present_foo'

And then execute:

$ bundle

Or install it yourself as:

$ gem install present_foo

Usage

Create your Presenters

Presenters are just classes that inherit from Presenter and have a name which matches the <Model>Presenter naming convention (later we'll see how to override this).

class Book < ActiveRecord::Base
  def some_model_method
    "foo"
  end
end

class BookPresenter < Presenter
  def some_presenter_method
    "bar"
  end
end

The Presenter base class inherits from SimpleDelegator, which allows instances of the presenter to mirror the public interface of the object they are presenting. For example, if you have a method on your presented object or model called some_model_method, you can call it directly on the presenter and it will be delegated to the wrapped object.

Presenters also all have a hook back to the controller they were created from. For example, if you need to get access to helpers or url generators you can do so from the controller method.

class BookPresenter < Presenter

  # Access to url generators
  def edit_url
    controller.edit_book_url
  end

  # Access to helper methods
  def permalink
    controller.create_permalink(self.title)
  end

end

You can also access the request or any other contextual data that's available to the controller in this manner.

Use Presenters in Controllers

In a controller action, you simply call present or present_many which sets an instance variable that can be used in views and also returns an instance of the presenter for use in non-html responses.

class BooksController < ApplicationController

  def index
    books = Book.all
    present_many books
  end

  def show
    book = Book.find(params[:id])
    present book
  end

end

# app/views/books/index.html.haml
%ul.books
  - @book_presenters.each do |book_presenter|
    %li= book_presenter.title

# app/views/books/show.html.haml
%h1= @book_presenter.title
%h3= @book_presenter.author

Extending Presenter Initialization

If you need to override the default behavior of a presenter at construction-time just override the initialize or new_list methods.

class BookPresenter < Presenter

  # Maps to present in controllers
  def initialize(obj, arg1, arg2)
    # ... do some more stuff
    super(obj)
  end

  # Maps to present_many in controllers
  def self.new_list(objs, arg1, arg2)
    # ... do some more stuff
    super(objs)
  end

end

In controllers additional arguments passed to present or present_many will be passed to these overridden constructor methods.

class BooksController < ApplicationController

  def index
    books = Books.all
    present_many books, "foo", "bar"
  end

end

Changing the Default Presenter Type

If you want to name your presenter something other than <Class>Presenter or, if you have more than one presenter for a given type you can simply pass the class you want to use as the second argument when calling present or present_many.

class BooksController < ApplicationController

  def index
    books = Books.all
    present_many books, OtherBookPresenter, "foo", "bar"
  end

end

TODO

1. Do something to assist with serialization scenarios
2. Make PresentFoo work in non-Rails environments

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