HasManyPrefetch

has_many_prefetch.rb

class HasManyPrefetch
  attr_reader :name
  attr_reader :values
  attr_reader :method_name
  attr_reader :fetcher

  def initialize(name:, method_name: nil, &fetcher)
    @name = name
    @method_name = method_name || "#{name}_id"
    @fetcher = fetcher
  end

  def fetch(collection)
    fetcher.call(collection.pluck(method_name).sort.uniq)
  end

  def bind(collection)
    values = fetch(collection)
    collection.each do |element|
      object_id = element[method_name]
      bind_object = values[object_id]
      element.define_singleton_method(name) { bind_object }
    end
  end
end