diff options
Diffstat (limited to 'activerecord/lib/active_record/inheritance.rb')
| -rw-r--r-- | activerecord/lib/active_record/inheritance.rb | 105 |
1 files changed, 81 insertions, 24 deletions
diff --git a/activerecord/lib/active_record/inheritance.rb b/activerecord/lib/active_record/inheritance.rb index 6ab67fdece..b91e9ac137 100644 --- a/activerecord/lib/active_record/inheritance.rb +++ b/activerecord/lib/active_record/inheritance.rb @@ -1,9 +1,42 @@ +require 'active_support/core_ext/hash/indifferent_access' + module ActiveRecord + # == Single table inheritance + # + # Active Record allows inheritance by storing the name of the class in a column that by + # default is named "type" (can be changed by overwriting <tt>Base.inheritance_column</tt>). + # This means that an inheritance looking like this: + # + # class Company < ActiveRecord::Base; end + # class Firm < Company; end + # class Client < Company; end + # class PriorityClient < Client; end + # + # When you do <tt>Firm.create(name: "37signals")</tt>, this record will be saved in + # the companies table with type = "Firm". You can then fetch this row again using + # <tt>Company.where(name: '37signals').first</tt> and it will return a Firm object. + # + # Be aware that because the type column is an attribute on the record every new + # subclass will instantly be marked as dirty and the type column will be included + # in the list of changed attributes on the record. This is different from non + # STI classes: + # + # Company.new.changed? # => false + # Firm.new.changed? # => true + # Firm.new.changes # => {"type"=>["","Firm"]} + # + # If you don't have a type column defined in your table, single-table inheritance won't + # be triggered. In that case, it'll work just like normal subclasses with no special magic + # for differentiating between them or reloading the right type with find. + # + # Note, all the attributes for all the cases are kept in the same table. Read more: + # http://www.martinfowler.com/eaaCatalog/singleTableInheritance.html + # module Inheritance extend ActiveSupport::Concern included do - # Determine whether to store the full constant name including namespace when using STI + # Determines whether to store the full constant name including namespace when using STI. class_attribute :store_full_sti_class, instance_writer: false self.store_full_sti_class = true end @@ -11,18 +44,26 @@ module ActiveRecord module ClassMethods # Determines if one of the attributes passed in is the inheritance column, # and if the inheritance column is attr accessible, it initializes an - # instance of the given subclass instead of the base class + # instance of the given subclass instead of the base class. def new(*args, &block) - if (attrs = args.first).is_a?(Hash) - if subclass = subclass_from_attrs(attrs) - return subclass.new(*args, &block) - end + if abstract_class? || self == Base + raise NotImplementedError, "#{self} is an abstract class and cannot be instantiated." + end + + attrs = args.first + if subclass_from_attributes?(attrs) + subclass = subclass_from_attributes(attrs) + end + + if subclass + subclass.new(*args, &block) + else + super end - # Delegate to the original .new - super end - # True if this isn't a concrete subclass needing a STI type condition. + # Returns +true+ if this does not need STI type condition. Returns + # +false+ if STI type condition needs to be applied. def descends_from_active_record? if self == Base false @@ -39,10 +80,12 @@ module ActiveRecord end def symbolized_base_class + ActiveSupport::Deprecation.warn('`ActiveRecord::Base.symbolized_base_class` is deprecated and will be removed without replacement.') @symbolized_base_class ||= base_class.to_s.to_sym end def symbolized_sti_name + ActiveSupport::Deprecation.warn('`ActiveRecord::Base.symbolized_sti_name` is deprecated and will be removed without replacement.') @symbolized_sti_name ||= sti_name.present? ? sti_name.to_sym : symbolized_base_class end @@ -108,16 +151,11 @@ module ActiveRecord candidates << type_name candidates.each do |candidate| - begin - constant = ActiveSupport::Dependencies.constantize(candidate) - return constant if candidate == constant.to_s - rescue NameError => e - # We don't want to swallow NoMethodError < NameError errors - raise e unless e.instance_of?(NameError) - end + constant = ActiveSupport::Dependencies.safe_constantize(candidate) + return constant if candidate == constant.to_s end - raise NameError, "uninitialized constant #{candidates.first}" + raise NameError.new("uninitialized constant #{candidates.first}", candidates.first) end end @@ -153,8 +191,8 @@ module ActiveRecord end def type_condition(table = arel_table) - sti_column = table[inheritance_column.to_sym] - sti_names = ([self] + descendants).map { |model| model.sti_name } + sti_column = table[inheritance_column] + sti_names = ([self] + descendants).map(&:sti_name) sti_column.in(sti_names) end @@ -163,18 +201,37 @@ module ActiveRecord # is not self or a valid subclass, raises ActiveRecord::SubclassNotFound # If this is a StrongParameters hash, and access to inheritance_column is not permitted, # this will ignore the inheritance column and return nil - def subclass_from_attrs(attrs) + def subclass_from_attributes?(attrs) + columns_hash.include?(inheritance_column) && attrs.is_a?(Hash) + end + + def subclass_from_attributes(attrs) subclass_name = attrs.with_indifferent_access[inheritance_column] - return nil if subclass_name.blank? || subclass_name == self.name - unless subclass = subclasses.detect { |sub| sub.name == subclass_name } - raise ActiveRecord::SubclassNotFound.new("Invalid single-table inheritance type: #{subclass_name} is not a subclass of #{name}") + + if subclass_name.present? && subclass_name != self.name + subclass = subclass_name.safe_constantize + + unless descendants.include?(subclass) + raise ActiveRecord::SubclassNotFound.new("Invalid single-table inheritance type: #{subclass_name} is not a subclass of #{name}") + end + + subclass end - subclass end end + def initialize_dup(other) + super + ensure_proper_type + end + private + def initialize_internals_callback + super + ensure_proper_type + end + # Sets the attribute used for single table inheritance to this class name if this is not the # ActiveRecord::Base descendant. # Considering the hierarchy Reply < Message < ActiveRecord::Base, this makes it possible to |