Resubject

Simple presenters built on Ruby's SimpleDelegator. Wrap your objects with presenter classes that add display logic while keeping your models clean.

Installation

Add to your Gemfile:

gem 'resubject', '~> 1.0'

Requires Ruby >= 3.1 and ActiveSupport >= 7.2.

Usage

Create a presenter by inheriting from Resubject::Presenter. All methods from the original object are available through delegation:

class Box < Struct.new(:name, :items)
end

class BoxPresenter < Resubject::Presenter
  def contents
    items.join(', ')
  end
end

box = Box.new('Awkward Package', ['platypus', 'sloth', 'anteater'])

presenter = BoxPresenter.new(box)
presenter.name     # => "Awkward Package" (delegated)
presenter.contents # => "platypus, sloth, anteater"

Collections

Wrap a collection of objects with Presenter.all:

boxes = [box1, box2, box3]
BoxPresenter.all(boxes)
# => [#<BoxPresenter>, #<BoxPresenter>, #<BoxPresenter>]

Nested presenters

Use presents to automatically wrap associated objects:

class PostPresenter < Resubject::Presenter
  presents :author                         # infers AuthorPresenter
  presents :comments, CommentPresenter     # explicit presenter class
end

post = PostPresenter.new(post)
post.author   # => #<AuthorPresenter>
post.comments # => [#<CommentPresenter>, ...]

Or use present inside a method for more control:

class PostPresenter < Resubject::Presenter
  def comments
    present(to_model.comments, CommentPresenter)
  end
end

Rails integration

Resubject includes a present helper in controllers and views automatically:

class BoxesController < ApplicationController
  def index
    @boxes = present(Box.all)
  end

  def show
    @box = present(Box.find(params[:id]))
  end
end

The helper resolves the presenter class by convention (Box -> BoxPresenter). You can also specify the presenter explicitly:

@boxes = present(Box.all, SpecialBoxPresenter)

Or stack multiple presenters:

@boxes = present(Box.all, BoxPresenter, ExtendedBoxPresenter)

Use present directly in views:

<%= present(@box).contents %>

ActionView helpers

Generate methods that delegate to ActionView helpers:

class ProductPresenter < Resubject::Presenter
  currency :price, precision: 2
  percentage :discount
  time_ago :published_at
  date_format :created_at, :short
end

product = ProductPresenter.new(product, view_context)
product.price        # => "$10.00"
product.discount     # => "25.000%"
product.published_at # => "about 1 hour"
product.created_at   # => "25 Dec 14:35"

Method	Maps to	Source
currency	number_to_currency	ActionView::Helpers::NumberHelper
percentage	number_to_percentage	ActionView::Helpers::NumberHelper
time_ago	time_ago_in_words	ActionView::Helpers::DateHelper
date_format	to_fs	ActiveSupport::TimeWithZone

Without Rails

Pass a template context manually when not using Rails:

require 'action_view'

presenter = PostPresenter.new(post, ActionView::Base.empty)

Testing

Resubject provides RSpec helpers that set up subject and template for specs in spec/presenters/:

# spec/presenters/user_presenter_spec.rb
require 'resubject/rspec'

describe UserPresenter do
  let(:object) { double(:user, first: 'Jane', last: 'Doe') }

  it 'has full name' do
    expect(subject.name).to eq 'Jane Doe'
  end
end

The subject is automatically created as described_class.new(object, template).

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes using conventional commits
4. Push to the branch (git push origin my-new-feature)
5. Create a Pull Request

License

MIT