The purpose of this gem is to handle the ajax calls made by the datatables plugin.

It parses some of the parameters (not all are yet supported) and returns the required data.

USAGE: To use this gem you will need to call the mapper class passing as arguments the model, parameters and a mapper. In this example, it is used a mapper which uses a partial view to render the actions column.

First, let's take a look at a piece of controller code:

def services_list
  respond_to do |format|
    format.json { render json: services_list_data }
  end
end

private

def services_list_data
  mapper = ModelMappers::ServiceMapper.new(service_actions)
  DatatablesRecordsMapper::Mapper
    .new(Service, params, mapper)
    .mapped_records
end

def service_actions
  @service_actions ||= Proc.new do |service|
    render_to_string(
      'actions',
      locals: { service_id: service.id },
      formats: :html,
      layout: false
    )
  end
end

This code is responsible for the endpoint 'GET services/services_list'. It instanciates a mapper for the model Service, which uses the service_acitons proc to render the actions column.

The mapper code:

module ModelMappers
  class ServiceMapper
    def initialize(actions_renderer)
      @actions_renderer = actions_renderer
    end

    def map(service)
      {
        id: service.id,
        title: service.title,
        description: service.description,
        actions: @actions_renderer.call(service)
      }
    end
  end
end

The only restriction in this class is the method 'map', which is used by the gem to return the data.

The actions partial view:

a.btn.btn-success.btn-margin-right title=(I18n.t 'links.default.actions.show') href=(service_path(service_id))
  span.fa.fa-search

The model code:

class Service < ActiveRecord::Base
  class << self
    def search(search_parameter, options)
      services = Service.all
      return services unless search_parameter.present?
      search_parameter = "%#{search_parameter.downcase}%"
      services.where('LOWER(title) like ? OR LOWER(description) like ?', search_parameter, search_parameter)
    end

    def paginate(services, limit, offset)
      services.
        order('id desc').
        limit(limit).
        offset(offset)
    end
  end
end