Simple Rails Presenter and View Presenter (so I don't forget)

presenter.rb

# frozen_string_literal: true

module Foo
  # Simple presenter module
  #
  # Uses Charlatan to create an `Foo::Presenter` module for use in the app.
  # This isn't *strictly* a presenter - it's somewhere between a presenter,
  # proxy, and/or decorator.
  #
  # Including `Foo::Presenter.new(:presented_thing)` in a class will
  # create a module (Charlatan inherits from Module) that, in turn, creates
  # an initializer so the proxied object is stored in the instance and
  # available through an instance method.
  #
  # Example:
  #   class MyPresenter
  #     include Foo::Presenter.new(:array)
  #
  #     def second_item
  #       array.second
  #     end
  #   end
  #
  #   array = [1, 2, 3]
  #   my_presenter = MyPresenter.new(array)
  #
  #   # available at the instance method
  #   my_presenter.array
  #   #=> [1, 2, 3]
  #
  #  # presenter appears *to be* the array
  #  my_presenter.length
  #  #=> 3
  #
  #  # can decorate with new methods
  #  my_presenter.second_item
  #  #=> 2
  class Presenter < Charlatan
  end
end

view_presenter.rb

# frozen_string_literal: true

module Foo
  # Simple presenter for view-related uses that mixes in some useful Rails
  # view helpers.
  #
  # Of note, the view presenter includes the Rails URL helpers so things like
  # `link_to` and `url_for` work. These are tricky helpers that require a few
  # dependencies and they have a very specific load order.
  #
  # See example in Foo::Presenter
  class ViewPresenter < Presenter
    def initialize(*args)
      super # let Charlatan do its thing

      include ActionView::Helpers::DateHelper
      include ActionView::Helpers::NumberHelper
      include ActionView::Helpers::SanitizeHelper
      include ActionView::Helpers::TextHelper
      include ActionView::Helpers::TranslationHelper
      include ActionView::Helpers::UrlHelper
      include InlineSvg::ActionView::Helpers
      include ApplicationHelper # bring in our global helpers
    end

    def included(mod)
      mod.extend ClassMethods
      mod.extend Sanitizers
      mod.include InstanceMethods
      mod.include Rails.application.routes.url_helpers
    end

    # Class methods(s) needed by various helpers
    module ClassMethods
      # Delegate the default urls options to ActionMailer
      def default_url_options
        ActionMailer::Base.default_url_options.merge(
          protocol: Rails.env.in?(%w[test development]) ? "http" : "https"
        )
      end

      def present_each(collection, *args, **kwargs)
        return unless collection.respond_to?(:map)

        collection.map { |item| new(item, *args, **kwargs) }
      end
    end

    # Instance method(s) needed by various helpers
    module InstanceMethods
      def present_collection(collection:, presenter:)
        collection.map { |item| presenter.new(item) }
      end

      # url helpers require options and default options or they override
      def url_options
        self.class.default_url_options
      end
      alias default_url_options url_options

      # return the value or a default
      def value_or_default(value, default = nil)
        value.present? ? value : default
      end
    end
  end

  # Sanitizer methods required by `SanitizeHelper`
  module Sanitizers
    def full_sanitizer
      @full_sanitizer ||= Rails::Html::FullSanitizer.new
    end

    def link_sanitizer
      @link_sanitizer ||= Rails::Html::LinkSanitizer.new
    end

    def white_list_sanitizer
      @white_list_sanitizer ||= Rails::Html::WhiteListSanitizer.new
    end
  end
end