Module: Rddd::Presenters

Defined in:

lib/rddd/presenters/presenter.rb,
lib/rddd/presenters/cacheable.rb,
lib/rddd/presenters/cache_entry.rb

Overview

Presenter is simply a view on the domain data. Presenters should be used each time, you are about to get some data out of the domain. The result returned from presenter should be either very dumb DTO (data transfer object) or one of the base data types like Array, Hash or even some scalar value.

Key goal is to make a clear boundary to the domain, so none full fledged business object is leaked outside of it.

Presenter output is composed inside “‘build“` method, which is called each time someone tries to access view “`data“`. Lets take a look at simple example:

class EventsByCityAndDatePresenter < Rddd::Presenters::View
  def initialize(city_id, date)
    @city_id = city_id
    @date = date

    super("#{city_id}-#{date}")
  end

  private

  def build
    format(City.find(@city_id).events_by_date(@date))
  end

  def format(events)
    events.map { |event| {:name => event.name, :time => event.time} }
  end
end

EventsByCityAndDatePresenter.new(city_id, Date.today).data #= [{:name => 'Happy new year!', :time => '00:00'}]

## Caching

So far we didn’t got too many benefits from use of the cache, although because the View made a clear boundary, there are some benefits which we can easily build on top of it. First is the caching. In order to plug it in simply extend Rddd::Presenters::Cacheable. See its documentation.

Defined Under Namespace

Modules: Cacheable, CacheableConfig Classes: CacheEntry, View