fetch_field.rb

# app/graph/fields/fetch_field.rb
class FetchField < GraphQL::Field
  def initialize(model:, type:)
    self.type = type
    @model = model
    self.description = 'Find a #{model.name} by ID'
    self.arguments = {
      'id' => GraphQL::Argument.define do
        name 'id'
        type !GraphQL::INT_TYPE
        description 'Id for record'
      end
    }
  end

  def resolve(_object, arguments, ctx)
    record = @model.find(arguments['id'])

    # Pundit authorization
    ctx[:pundit].authorize record, :show?

    record
  rescue Pundit::NotAuthorizedError
    GraphQL::ExecutionError.new("Unauthorized: Show #{@model.name}")
  end
end