gem 'graphql-batch'

$ bundle

$ gem install graphql-batch

require 'graphql/batch'

class RecordLoader < GraphQL::Batch::Loader
  def initialize(model)
    @model = model
  end

  def perform(ids)
    @model.where(id: ids).each { |record| fulfill(record.id, record) }
    ids.each { |id| fulfill(id, nil) unless fulfilled?(id) }
  end
end

MySchema = GraphQL::Schema.define do
  query MyQueryType

  use GraphQL::Batch
end

MySchema = GraphQL::Schema.define do
  query MyQueryType

  GraphQL::Batch.use(self)
end

resolve -> (obj, args, context) { RecordLoader.for(Product).load(args["id"]) }

resolve -> (obj, args, context) do
  RecordLoader.for(Product).load(args["id"]).then do |product|
    product.title
  end
end

resolve -> (obj, args, context) do
  RecordLoader.for(Product).load(args["id"]).then do |product|
    RecordLoader.for(Image).load(product.image_id)
  end
end

resolve -> (obj, args, context) do
  Promise.all([
    CountLoader.for(Shop, :smart_collections).load(context.shop_id),
    CountLoader.for(Shop, :custom_collections).load(context.shop_id),
  ]).then do |results|
    results.reduce(&:+)
  end
end

resolve -> (obj, args, context) do
  CacheLoader.for(Product).load(args["id"]).then(nil, lambda do |exc|
    raise exc unless exc.is_a?(Redis::BaseConnectionError)
    logger.warn err.message
    RecordLoader.for(Product).load(args["id"])
  end)
end

  def test_single_query
    product = products(:snowboard)
    title = GraphQL::Batch.batch do
      RecordLoader.for(Product).load(product.id).then(&:title)
    end
    assert_equal product.title, title
  end