1-project_type.rb

module Types
  ProjectType = GraphQL::ObjectType.define do
    name "Project"
    description "a project"
    
    implements GraphQL::Relay::Node.interface

    global_id_field :id

    field :title, !types.String do
      resolve ->(project, args, ctx) { project.user.email.split('@')[0] + '-' + project.title }
    end

    field :user, !UserType
    
    connection :tasks, TaskType.connection_type
  end
end

2-task_type.rb

module Types
  TaskType = GraphQL::ObjectType.define do
    name "Task"
    description "a task"
    
    implements GraphQL::Relay::Node.interface

    global_id_field :id

    field :title, !types.String
    field :completed, !types.Boolean

    field :project, !ProjectType
  end
end

3-query.graphql

query {
  projects {
    id
    title
    
    tasks {
      edges {
        node {
          id
          title
          completed
        }
      }
    }
  }
}