require 'active_support/core_ext/object/deep_dup' module ActiveRecord # Declare an enum attribute where the values map to integers in the database, # but can be queried by name. Example: # # class Conversation < ActiveRecord::Base # enum status: [ :active, :archived ] # end # # # conversation.update! status: 0 # conversation.active! # conversation.active? # => true # conversation.status # => "active" # # # conversation.update! status: 1 # conversation.archived! # conversation.archived? # => true # conversation.status # => "archived" # # # conversation.update! status: 1 # conversation.status = "archived" # # # conversation.update! status: nil # conversation.status = nil # conversation.status.nil? # => true # conversation.status # => nil # # Scopes based on the allowed values of the enum field will be provided # as well. With the above example: # # Conversation.active # Conversation.archived # # Of course, you can also query them directly if the scopes don't fit your # needs: # # Conversation.where(status: [:active, :archived]) # Conversation.where.not(status: :active) # # You can set the default value from the database declaration, like: # # create_table :conversations do |t| # t.column :status, :integer, default: 0 # end # # Good practice is to let the first declared status be the default. # # Finally, it's also possible to explicitly map the relation between attribute and # database integer with a +Hash+: # # class Conversation < ActiveRecord::Base # enum status: { active: 0, archived: 1 } # end # # Note that when an +Array+ is used, the implicit mapping from the values to database # integers is derived from the order the values appear in the array. In the example, # :active is mapped to +0+ as it's the first element, and :archived # is mapped to +1+. In general, the +i+-th element is mapped to i-1 in the # database. # # Therefore, once a value is added to the enum array, its position in the array must # be maintained, and new values should only be added to the end of the array. To # remove unused values, the explicit +Hash+ syntax should be used. # # In rare circumstances you might need to access the mapping directly. # The mappings are exposed through a class method with the pluralized attribute # name, which return the mapping in a +HashWithIndifferentAccess+: # # Conversation.statuses[:active] # => 0 # Conversation.statuses["archived"] # => 1 # # Use that class method when you need to know the ordinal value of an enum. # For example, you can use that when manually building SQL strings: # # Conversation.where("status <> ?", Conversation.statuses[:archived]) # module Enum def self.extended(base) # :nodoc: base.class_attribute(:defined_enums) base.defined_enums = {} end def inherited(base) # :nodoc: base.defined_enums = defined_enums.deep_dup super end class EnumType < Type::Value def initialize(name, mapping) @name = name @mapping = mapping end def cast(value) return if value.blank? if mapping.has_key?(value) value.to_s elsif mapping.has_value?(value) mapping.key(value) else raise ArgumentError, "'#{value}' is not a valid #{name}" end end def deserialize(value) return if value.nil? mapping.key(value.to_i) end def serialize(value) mapping.fetch(value, value) end protected attr_reader :name, :mapping end def enum(definitions) klass = self definitions.each do |name, values| # statuses = { } enum_values = ActiveSupport::HashWithIndifferentAccess.new name = name.to_sym # def self.statuses statuses end detect_enum_conflict!(name, name.to_s.pluralize, true) klass.singleton_class.send(:define_method, name.to_s.pluralize) { enum_values } detect_enum_conflict!(name, name) detect_enum_conflict!(name, "#{name}=") attribute name, EnumType.new(name, enum_values) _enum_methods_module.module_eval do pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index pairs.each do |value, i| enum_values[value] = i # def active?() status == 0 end klass.send(:detect_enum_conflict!, name, "#{value}?") define_method("#{value}?") { self[name] == value.to_s } # def active!() update! status: :active end klass.send(:detect_enum_conflict!, name, "#{value}!") define_method("#{value}!") { update! name => value } # scope :active, -> { where status: 0 } klass.send(:detect_enum_conflict!, name, value, true) klass.scope value, -> { klass.where name => value } end end defined_enums[name.to_s] = enum_values end end private def _enum_methods_module @_enum_methods_module ||= begin mod = Module.new include mod mod end end ENUM_CONFLICT_MESSAGE = \ "You tried to define an enum named \"%{enum}\" on the model \"%{klass}\", but " \ "this will generate a %{type} method \"%{method}\", which is already defined " \ "by %{source}." def detect_enum_conflict!(enum_name, method_name, klass_method = false) if klass_method && dangerous_class_method?(method_name) raise ArgumentError, ENUM_CONFLICT_MESSAGE % { enum: enum_name, klass: self.name, type: 'class', method: method_name, source: 'Active Record' } elsif !klass_method && dangerous_attribute_method?(method_name) raise ArgumentError, ENUM_CONFLICT_MESSAGE % { enum: enum_name, klass: self.name, type: 'instance', method: method_name, source: 'Active Record' } elsif !klass_method && method_defined_within?(method_name, _enum_methods_module, Module) raise ArgumentError, ENUM_CONFLICT_MESSAGE % { enum: enum_name, klass: self.name, type: 'instance', method: method_name, source: 'another enum' } end end end end