Hi Dave, I really appreciate the effort in putting into this.

I am having a challenge with .methods, when I call the book or the shelf methods the output is totally different, what could be the issue?

03:0> @book.methods :shelf_ids=, :shelves, :authors, :description, :authors=, :id_came_from_user?, :id_previously_changed?, :id_changed?, :id_change, :id_will_change!, :id_previous_change, :id_previously_was, :restore_id!, :clear_id_change, :saved_change_to_id?, :saved_change_to_id, :id_before_last_save, :will_save_change_to_id?, :id_change_to_be_saved, :title_before_type_cast, :title_for_database, :title_came_from_user?, :title?, :title_previously_changed?, :title_changed?, :title_change, :title_will_change!, :title_was, :title_previous_change, :title_previously_was, :restore_title!, :clear_title_change, :saved_change_to_title?, :saved_change_to_title, :title_before_last_save, :will_save_change_to_title?, :title_change_to_be_saved, :title_in_database, :authors_before_type_cast, :authors_for_database, :authors_came_from_user?, :authors?, :authors_previously_changed?, :authors_changed?, :authors_change, :authors_will_change!, :authors_was, :authors_previous_change, :authors_previously_was, :restore_authors!, :clear_authors_change, :saved_change_to_authors?, :saved_change_to_authors, :authors_before_last_save, :will_save_change_to_authors?, :authors_change_to_be_saved, :authors_in_database, :description_before_type_cast, :description_for_database, :description_came_from_user?, :description?, :description_previously_changed?, :description_changed?, :description_change, :description_will_change!, :description_was, :description_previous_change, :description_previously_was, :restore_description!, :clear_description_change, :saved_change_to_description?, :title, :saved_change_to_description, :description_before_last_save, :will_save_change_to_description?, :description_change_to_be_saved, :description_in_database, :page_count_before_type_cast, :page_count_for_database, :page_count_came_from_user?, :page_count?, :page_count_previously_changed?, :page_count_changed?, :page_count_change, :page_count_will_change!, :page_count_was, :page_count_previous_change, :page_count_previously_was, :restore_page_count!, :clear_page_count_change, :saved_change_to_page_count?, :saved_change_to_page_count, :page_count_before_last_save, :will_save_change_to_page_count?, :page_count_change_to_be_saved, :page_count_in_database, :categories_before_type_cast, :categories_for_database, :categories_came_from_user?, :categories?, :categories_previously_changed?, :categories_changed?, :categories_change, :categories_will_change!, :categories_was, :categories_previous_change, :categories_previously_was, :restore_categories!, :clear_categories_change, :saved_change_to_categories?, :saved_change_to_categories, :categories_before_last_save, :will_save_change_to_categories?, :categories_change_to_be_saved, :categories_in_database, :image_links_before_type_cast, :image_links_for_database, :image_links_came_from_user?, :image_links?, :image_links_previously_changed?, :image_links_changed?, :image_links_change, :image_links_will_change!, :image_links_was, :image_links_previous_change, :image_links_previously_was, :restore_image_links!, :clear_image_links_change, :saved_change_to_image_links?, :saved_change_to_image_links, :image_links_before_last_save, :will_save_change_to_image_links?, :image_links_change_to_be_saved, :image_links_in_database, :created_at_before_type_cast, :created_at_for_database, :created_at_came_from_user?, :created_at?, :created_at_previously_changed?, :created_at_changed?, :created_at_change, :created_at_will_change!, :created_at_was, :created_at_previous_change, :created_at_previously_was, :restore_created_at!, :clear_created_at_change, :saved_change_to_created_at?, :saved_change_to_created_at, :created_at_before_last_save, :will_save_change_to_created_at?, :created_at_change_to_be_saved, :created_at_in_database, :updated_at_for_database, :updated_at?, :updated_at_changed?, :updated_at_change, :updated_at_will_change!, :updated_at_was, :updated_at_previous_change, :updated_at_previously_was, :restore_updated_at!, :clear_updated_at_change, :saved_change_to_updated_at?, :saved_change_to_updated_at, :updated_at_before_last_save, :will_save_change_to_updated_at?, :updated_at_change_to_be_saved, :updated_at_in_database, :updated_at_previously_changed?, :page_count=, :categories=, :page_count, :categories, :image_links, :created_at=, :updated_at=, :image_links=, :description=, :updated_at, :updated_at_before_type_cast, :title=, :updated_at_came_from_user?, :created_at, :encrypt, :decrypt, :logger, :_update_callbacks, :_destroy_callbacks, :record_timestamps=, :attribute_method_matchers, :defined_enums?, :encrypted_attributes, :destroy_association_async_job, :primary_key_prefix_type, :encrypted_attributes?, :attachment_reflections, :table_name_prefix, :_reflections, :aggregate_reflections, :automatic_scope_inversing, :default_role, :default_shard, :_run_initialize_callbacks, :_run_find_callbacks, :table_name_suffix, :primary_key_prefix_type?, :_validate_callbacks, :table_name_prefix?, :_validators?, :logger?, :table_name_suffix?, :attachment_reflections?, :default_connection_handler?, :pluralize_table_names?, :default_role?, :default_shard?, :store_full_class_name, :store_full_sti_class, :lock_optimistically, :lock_optimistically?, :attribute_aliases?, :store_full_class_name?, :nested_attributes_options, :attribute_method_matchers?, :store_full_sti_class?, :pluralize_table_names, :default_scopes, :default_scope_override, :defined_enums, :record_timestamps, :time_zone_aware_attributes, :skip_time_zone_conversion_for_attributes, :time_zone_aware_types, :nested_attributes_options?, :time_zone_aware_attributes?, :skip_time_zone_conversion_for_attributes?, :time_zone_aware_types?, :partial_updates, :partial_inserts, :cache_versioning, :callbacks, :partial_updates?, :partial_inserts?, :_run_commit_callbacks, :_run_rollback_callbacks, :_run_before_commit_callbacks, :cache_timestamp_format, :collection_cache_versioning, :_rollback_callbacks, :_commit_callbacks, :cache_timestamp_format?, :_before_commit_callbacks, :cache_versioning?, :collection_cache_versioning?, :default_connection_handler, :validation_context, :_validators, :model_name, :_reflections?, :aggregate_reflections?, :automatic_scope_inversing?, :_run_validate_callbacks, :include_root_in_json, :signed_id_verifier_secret, :include_root_in_json?, :_run_validation_callbacks, :attribute_aliases, :type_for_attribute, :_run_destroy_callbacks, :record_timestamps?, :_run_touch_callbacks, :_run_save_callbacks, :_run_create_callbacks, :_run_update_callbacks, :_validation_callbacks, :_initialize_callbacks, :callbacks?, :_find_callbacks, :signed_id_verifier_secret?, :_touch_callbacks, :encrypted_attributes=, :column_for_attribute, :_save_callbacks, :_create_callbacks, :attachment_changes, :reload, :changed_for_autosave?, :to_global_id, :to_gid, :to_signed_global_id, :to_sgid, :to_sgid_param, :to_gid_param, :encrypted_attribute?, :ciphertext_for, :save, :save!, :signed_id, :serializable_hash, :as_json, :from_json, :read_attribute_for_serialization, :attribute_names, :touch, :no_touching?, :touch_later, :before_committed!, :destroy, :rolledback!, :trigger_transactional_callbacks?, :transaction, :with_transaction_returning_status, :committed!, :_destroy, :mark_for_destruction, :destroyed_by_association=, :marked_for_destruction?, :destroyed_by_association, :association, :association_cached?, :increment!, :will_save_change_to_attribute?, :saved_change_to_attribute?, :saved_change_to_attribute, :attribute_before_last_save, :saved_changes?, :saved_changes, :has_changes_to_save?, :attribute_change_to_be_saved, :changes_to_save, :changed_attribute_names_to_save, :attributes_in_database, :attribute_in_database, :changes, :previous_changes, :changed, :clear_changes_information, :changed?, :attribute_changed_in_place?, :clear_attribute_changes, :changes_applied, :attribute_changed?, :attribute_previously_changed?, :attribute_previously_was, :restore_attributes, :attribute_was, :changed_attributes, :id_in_database, :to_key, :id_for_database, :id=, :id?, :id_was, :id, :id_before_type_cast, :query_attribute, :read_attribute_before_type_cast, :attributes_before_type_cast, :attributes_for_database, :_write_attribute, :write_attribute, :read_attribute, :_read_attribute, :attributes, :_has_attribute?, :attribute_for_inspect, :[], :[]=, :attribute_present?, :accessed_fields, :respond_to?, :has_attribute?, :method_missing, :respond_to_without_attributes?, :attribute_missing, :lock!, :with_lock, :locking_enabled?, :valid?, :validate, :validates_inclusion_of, :validates_numericality_of, :validates_presence_of, :validates_length_of, :validates_confirmation_of, :validates_size_of, :validates_absence_of, :validates_comparison_of, :validates_exclusion_of, :validates_acceptance_of, :validates_format_of, :run_callbacks, :errors, :read_attribute_for_validation, :validates_with, :validate!, :invalid?, :cache_key_with_version, :cache_key, :cache_version, :to_param, :to_model, :to_partial_path, :assign_attributes, :attributes=, :populate_with_current_scope_attributes, :initialize_internals_callback, :decrement!, :toggle, :toggle!, :persisted?, :update!, :delete, :previously_new_record?, :previously_persisted?, :destroyed?, :destroy!, :becomes, :becomes!, :increment, :decrement, :update_attribute, :update, :update_column, :update_columns, :new_record?, :strict_loading!, :strict_loading_mode, :strict_loading_n_plus_one_only?, :<=>, :readonly!, :==, :blank?, :pretty_print, :values_at, :eql?, :readonly?, :present?, :encode_with, :freeze, :inspect, :slice, :strict_loading?, :connection_handler, :frozen?, :init_with_attributes, :init_with, :hash, :untaint, :require_dependency, :to_json, :instance_values, :instance_variable_names, :in?, :presence_in, :binding, :to_yaml, :presence, :deep_dup, :with_options, :acts_like?, :duplicable?, :html_safe?, :to_query, :pry, :pretty_print_inspect, :pretty_print_cycle, :pretty_print_instance_variables, :try!, :try, :singleton_class, :dup, :itself, :taint, :tainted?, :untrust, :untrusted?, :trust, :methods, :singleton_methods, :protected_methods, :private_methods, :public_methods, :instance_variables, :instance_variable_get, :instance_variable_set, :instance_variable_defined?, :remove_instance_variable, :instance_of?, :kind_of?, :is_a?, :display, :pretty_inspect, :class, :tap, :then, :yield_self, :gem, :public_send, :class_eval, :extend, :clone, :method, :public_method, :singleton_method, :define_singleton_method, :===, :=~, :!~, :nil?, :object_id, :send, => [:autosave_associated_records_for_shelvings, :validate_associated_records_for_shelvings, :autosave_associated_records_for_books,
:validate_associated_records_for_books,
:books,ce_eval, :shelving_ids,, :shelvings=, :shelving_ids=, :book_ids, :books=,:004:0> @shelf.methods :shelvings, :book_ids=, :clear_created_at_change, :saved_change_to_created_at?, :created_at_previous_change, :created_at_previously_changed?, :restore_created_at!, :created_at_change_to_be_saved, :created_at_in_database, :saved_change_to_created_at, :created_at_before_last_save, :created_at_previously_was, :updated_at_changed?, :updated_at_change, :updated_at_for_database, :updated_at?, :updated_at_previously_changed?, :will_save_change_to_created_at?, :restore_updated_at!, :updated_at_will_change!, :updated_at_was, :updated_at_previous_change, :updated_at_previously_was, :will_save_change_to_updated_at?, :clear_updated_at_change, :saved_change_to_updated_at?, :saved_change_to_updated_at, :updated_at_before_last_save, :updated_at, :name_before_type_cast, :name_for_database, :name_came_from_user?, :name?, :name_previously_changed?, :name_changed?, :name_change, :name_will_change!, :name_was, :name_previous_change, :name_previously_was, :restore_name!, :clear_name_change, :saved_change_to_name?, :saved_change_to_name, :name_before_last_save, :will_save_change_to_name?, :name_change_to_be_saved, :name_in_database, :updated_at=, :updated_at_before_type_cast, :updated_at_change_to_be_saved, :updated_at_in_database, :updated_at_came_from_user?, :name=, :created_at=, :created_at, :name, :id_came_from_user?, :created_at_for_database, :created_at_came_from_user?, :created_at?, :id_previously_changed?, :id_changed?, :created_at_change, :created_at_will_change!, :created_at_was, :id_change, :id_will_change!, :id_previous_change, :id_previously_was, :restore_id!, :clear_id_change, :saved_change_to_id?, :saved_change_to_id, :id_before_last_save, :will_save_change_to_id?, :id_change_to_be_saved, :created_at_changed?, :created_at_before_type_cast, :encrypt, :decrypt, :logger, :_update_callbacks, :_destroy_callbacks, :record_timestamps=, :attribute_method_matchers, :defined_enums?, :encrypted_attributes, :destroy_association_async_job, :primary_key_prefix_type, :encrypted_attributes?, :attachment_reflections, :table_name_prefix, :_reflections, :aggregate_reflections, :automatic_scope_inversing, :default_role, :default_shard, :_run_initialize_callbacks, :_run_find_callbacks, :table_name_suffix, :primary_key_prefix_type?, :_validate_callbacks, :table_name_prefix?, :_validators?, :logger?, :table_name_suffix?, :attachment_reflections?, :default_connection_handler?, :pluralize_table_names?, :default_role?, :default_shard?, :store_full_class_name, :store_full_sti_class, :lock_optimistically, :lock_optimistically?, :attribute_aliases?, :store_full_class_name?, :nested_attributes_options, :attribute_method_matchers?, :store_full_sti_class?, :pluralize_table_names, :default_scopes, :default_scope_override, :defined_enums, :record_timestamps, :time_zone_aware_attributes, :skip_time_zone_conversion_for_attributes, :time_zone_aware_types, :nested_attributes_options?, :time_zone_aware_attributes?, :skip_time_zone_conversion_for_attributes?, :time_zone_aware_types?, :partial_updates, :partial_inserts, :cache_versioning, :callbacks, :partial_updates?, :partial_inserts?, :_run_commit_callbacks, :_run_rollback_callbacks, :_run_before_commit_callbacks, :cache_timestamp_format, :collection_cache_versioning, :_rollback_callbacks, :_commit_callbacks, :cache_timestamp_format?, :_before_commit_callbacks, :cache_versioning?, :collection_cache_versioning?, :default_connection_handler, :validation_context, :_validators, :model_name, :_reflections?, :aggregate_reflections?, :automatic_scope_inversing?, :_run_validate_callbacks, :include_root_in_json, :signed_id_verifier_secret, :include_root_in_json?, :_run_validation_callbacks, :attribute_aliases, :type_for_attribute, :_run_destroy_callbacks, :record_timestamps?, :_run_touch_callbacks, :_run_save_callbacks, :_run_create_callbacks, :_run_update_callbacks, :_validation_callbacks, :_initialize_callbacks, :callbacks?, :_find_callbacks, :signed_id_verifier_secret?, :_touch_callbacks, :encrypted_attributes=, :column_for_attribute, :_save_callbacks, :_create_callbacks, :attachment_changes, :reload, :changed_for_autosave?, :to_global_id, :to_gid, :to_signed_global_id, :to_sgid, :to_sgid_param, :to_gid_param, :encrypted_attribute?, :ciphertext_for, :save, :save!, :signed_id, :serializable_hash, :as_json, :from_json, :read_attribute_for_serialization, :attribute_names, :touch, :no_touching?, :touch_later, :before_committed!, :destroy, :rolledback!, :trigger_transactional_callbacks?, :transaction, :with_transaction_returning_status, :committed!, :_destroy, :mark_for_destruction, :destroyed_by_association=, :marked_for_destruction?, :destroyed_by_association, :association, :association_cached?, :increment!, :will_save_change_to_attribute?, :saved_change_to_attribute?, :saved_change_to_attribute, :attribute_before_last_save, :saved_changes?, :saved_changes, :has_changes_to_save?, :attribute_change_to_be_saved, :changes_to_save, :changed_attribute_names_to_save, :attributes_in_database, :attribute_in_database, :changes, :previous_changes, :changed, :clear_changes_information, :changed?, :attribute_changed_in_place?, :clear_attribute_changes, :changes_applied, :attribute_changed?, :attribute_previously_changed?, :attribute_previously_was, :restore_attributes, :attribute_was, :changed_attributes, :id_in_database, :to_key, :id_for_database, :id=, :id?, :id_was, :id, :id_before_type_cast, :query_attribute, :read_attribute_before_type_cast, :attributes_before_type_cast, :attributes_for_database, :_write_attribute, :write_attribute, :read_attribute, :_read_attribute, :attributes, :_has_attribute?, :attribute_for_inspect, :[], :[]=, :attribute_present?, :accessed_fields, :respond_to?, :has_attribute?, :method_missing, :respond_to_without_attributes?, :attribute_missing, :lock!, :with_lock, :locking_enabled?, :valid?, :validate, :validates_inclusion_of, :validates_numericality_of, :validates_presence_of, :validates_length_of, :validates_confirmation_of, :validates_size_of, :validates_absence_of, :validates_comparison_of, :validates_exclusion_of, :validates_acceptance_of, :validates_format_of, :run_callbacks, :errors, :read_attribute_for_validation, :validates_with, :validate!, :invalid?, :cache_key_with_version, :cache_key, :cache_version, :to_param, :to_model, :to_partial_path, :assign_attributes, :attributes=, :populate_with_current_scope_attributes, :initialize_internals_callback, :decrement!, :toggle, :toggle!, :persisted?, :update!, :delete, :previously_new_record?, :previously_persisted?, :destroyed?, :destroy!, :becomes, :becomes!, :increment, :decrement, :update_attribute, :update, :update_column, :update_columns, :new_record?, :strict_loading!, :strict_loading_mode, :strict_loading_n_plus_one_only?, :<=>, :readonly!, :==, :blank?, :pretty_print, :values_at, :eql?, :readonly?, :present?, :encode_with, :freeze, :inspect, :slice, :strict_loading?, :connection_handler, :frozen?, :init_with_attributes, :init_with, :hash, :untaint, :require_dependency, :to_json, :instance_values, :instance_variable_names, :in?, :presence_in, :binding, :to_yaml, :presence, :deep_dup, :with_options, :acts_like?, :duplicable?, :html_safe?, :to_query, :pry, :pretty_print_inspect, :pretty_print_cycle, :pretty_print_instance_variables, :try!, :try, :singleton_class, :dup, :itself, :taint, :tainted?, :untrust, :untrusted?, :trust, :methods, :singleton_methods, :protected_methods, :private_methods, :public_methods, :instance_variables, :instance_variable_get, :instance_variable_set, :instance_variable_defined?, :remove_instance_variable, :instance_of?, :kind_of?, :is_a?, :display, :pretty_inspect, :class, :tap, :then, :yield_self, :gem, :public_send, :class_eval, :extend, :clone, :method, :public_method, :singleton_method, :define_singleton_method, :===, :=~, :!~, :nil?, :object_id, :send, :to_enum, :enum_for, :to_s, :send, :!, :instance_eval, :instance_exec, :!=, :equal?, :id]