Frosting

Let's simplify using presenters in Rails.

Add gem "frosting" to your Gemfile and run bundle install.

You have a Post model. You're a good lil' rabbit, and it only contains methods concerned with its persistence.

So where do you put presentation-specific logic?

The view, right? Nah, man. You should probably use a presenter.

Let's say we're in PostsController#show and you want to implement some sort of presentation logic. How about we're color coding based on the age of the post.

If you present @post from your controller (and its class is Post), frosting will look for Presenters::Post (defined in /models/presenters/post.rb presumably). Here's what that could look like:

module Presenters
  class Post < Frosting::BasePresenter
    def color
      old? ? 'red' : 'green'
    end
  end
end

You defined #old? in your model because it's not a presentation concern. Good job.

Frosting::BasePresenter delegates to the resource you're presenting, and it also has access to the view context. It doesn't delegate anything by default, but you can delegate things like link_to and content_tag if it makes your life easier. You should probably make your own base presenter that inherits from frosting's base. It's your life, and you should do what you want to.

You can also call present_collection @posts should you be dealing with a collection of posts and want them all to be presented.

As an additional trick, if you find yourself writing code like:

def user
  present super(), context: @context
end

in order to have your presented Post return a presenter for the associated User, then you can save some typing with:

presents_super :user

The presents_super method accepts options, so you can specify a presenter:

presents_super :user, presenter: SomeCustomPresenter

You can also use presents_super for collections, by passing the collection option:

presents_super :users, collection: true

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