Full stack Lotus application example

README.md

Lotus

The Lotus gem wasn't released yet, but all the core frameworks are out at the version 0.1.0. This is a guide to build a full stack Lotus application today.

Installation

Clone this gist:

% git clone https://gist.github.com/9830002.git lotus

Setup:

% cd lotus && bash setup.sh

Run the specs:

% bundle exec rake

Architecture

This guide has two files to look at:

1. lotus.rb
2. application.rb

Lotus

The code in this file is a simplfied version of the gem that will be released in the near future.

Lotus' frameworks are known to have few conventions and they are agnostic by design. This characteristic let them to be used in already existing projects.

However, I want Lotus apps to be different. They will take small decisions for the developers, in order to help in their day to day work.

For this reason, Lotus gem brings some behind the scenes enhancements of their capabilities. It will inject glue code to make all the components to work together.

One case is Lotus::View.load!: I don't expect developers to deal with this low level details, Lotus will do this job for you.

This is the meaning of the FullStackPatch module, it adds some behaviors to Lotus::Action.

Another convention that you will see is the matching between action and view names (see RenderingPolicy). Given a HomeController::Index, Lotus expects to find Home::Index view. This mechanism may not match your thinking, that's why a Lotus::Application let to inject this policy.

Application

What you see here is the code of a Lotus application. Generally, all these classes are split across files, but here I kept them together to emphatize the matching parts.

HomeController::Index is a typical example of Lotus::Controller. When called, it sets the value of @planet, it will be available accesible using #planet or #exposures.

The most important aspect of Home::Index is #greet. The implementation of this method uses a concrete method #salutation with something that cames from the action: #planet.

That information can be accessed here because Action#to_rendering returns a context that matches Lotus::View needs (see Lotus::View::Rendering#render).

If you try:

action = HomeController::Index.new
action.call({'HTTP_ACCEPT' => 'text/html'})

action.to_rendering # => { planet: 'World', format: :html }

That output is exactly what Home::Index.render expects.

The rest of the file deals with loading mechanisms and a compatibility with Rack::Builder.

Please notice that Application constant is assigned as Capybara.app in spec/spec_helper.rb. This makes possible to run features tests with RSpec.

Feedback

If you have any question or feedback, please leave a comment here or ping me on Twitter: @jodosha.

Happy hacking!

application.rb

require 'lotus/router'
require 'lotus/controller'
require 'lotus/view'
require_relative 'lotus'

class HomeController
  include Lotus::Controller

  action 'Index' do
    expose :planet

    def call(params)
      @planet = 'World'
    end
  end
end

module Home
  class Index
    include Lotus::View

    def salutation
      'Hello'
    end

    def greet
      "#{ salutation }, #{ planet }!"
    end
  end
end

Lotus::View.root = __dir__ + '/templates'
Lotus::View.load!

router = Lotus::Router.new do
  get '/', to: 'home#index'
end

Application = Rack::Builder.new do
  run Lotus::Application.new(router)
end.to_app

Gemfile

source 'https://rubygems.org'

gem 'rake'
gem 'lotus-router'
gem 'lotus-controller'
gem 'lotus-view'

group :test do
  gem 'rspec'
  gem 'capybara'
end

home_page_spec.rb

require 'spec_helper'

feature 'Home page' do
  it 'successfully visits the home page' do
    visit '/'

    expect(page.body).to match('Hello, World!')
  end
end

index.html.erb

<%= greet %>

lotus.rb

module FullStackPatch
  def response
    [ super, self ].flatten
  end

  def format
    Rack::Mime::MIME_TYPES.invert[content_type].gsub(/\A\./, '').to_sym
  end

  def to_rendering
    exposures.merge(format: format)
  end
end

Lotus::Action::Rack.class_eval do
  prepend FullStackPatch
end

module Lotus
  class Application
    def initialize(router, renderer = RenderingPolicy.new)
      @router   = router
      @renderer = renderer
    end

    def call(env)
      _call(env).tap do |response|
        response[2] = Array(@renderer.render(response))
      end
    end

    private
    def _call(env)
      env['HTTP_ACCEPT'] ||= 'text/html'
      @router.call(env)
    end
  end

  class RenderingPolicy
    def render(response)
      if render?(response)
        action = response.pop
        view   = view_for(action)
        view.render(action.to_rendering)
      end
    end

    private
    def render?(response)
      response.last.respond_to?(:to_rendering)
    end

    def view_for(action)
      Object.const_get(action.class.name.gsub(/Controller/, ''))
    end
  end
end

Rakefile

require 'rspec/core/rake_task'

RSpec::Core::RakeTask.new(:spec)
task default: :spec

task :server do
  exec 'bundle exec rackup application.rb'
end

setup.sh

#!/bin/bash
mkdir -p spec/features
mkdir -p templates/home

mv spec_helper.rb    spec
mv home_page_spec.rb spec/features
mv index.html.erb    templates/home

bundle

# This script will self destruct in 3, 2, 1.. poof!
rm -- "$0"

spec_helper.rb

$:.unshift __dir__ + '/..'
require 'rubygems'
require 'bundler'
Bundler.require(:default, :test)
require 'rspec'
require 'capybara/rspec'
require 'application'

module RSpec
  module FeatureExampleGroup
    def self.included(group)
      group.metadata[:type] = :feature
      Capybara.app = Application
    end
  end
end

RSpec.configure do |c|
  def c.escaped_path(*parts)
    Regexp.compile(parts.join('[\\\/]') + '[\\\/]')
  end

  c.color = true

  c.include RSpec::FeatureExampleGroup, type: :feature, example_group: {
    file_path: c.escaped_path(%w[spec features])
  }

  c.include Capybara::DSL, type: :feature
end

Lotus gem is awesome, but since it stick together all parts of lotus microframeworks, I can't figure out how to exclude views from some app (API, for example) and keep it for others.